The DM controls treasure…
The Dungeon Master's Guide (1979) on Placement of Monetary Treasure says
All monsters would not and should not possess treasure! The treasure types given in the Monster Manual are the optimums and ore meant to consider the maximum number of creatures guarding them. Many of the monsters shown as possessing some form of wealth are quite unlikely to have any at all. This is not a contradiction in the rules, but an admonition to the DM not to give away too much! Any treasure possessed by weak, low-level monsters will be trifling compared to what numbers of stronger monsters might guard. So in distributing wealth amongst the creatures which inhabit the upper levels of dungeons/dungeon-like areas, as well as for petty monsters dwelling in small numbers in the wilderness, assign it accordingly. The bulk of such treasure will be copper pieces and silver. Perhaps there will be a bit of ivory or a cunningly-crafted item worth a few gold pieces. (91-2)
The section then details how the DM places monetary treasure. This is followed by a section describing the placement of magic items (92-3). Neither section encourages slavish adherence to random treasure table rolls and, on the contrary, recommends the DM place (not roll) monetary and magical treasure based on the creatures encountered and the player characters themselves.
So the DM decides what treasure exists not the dice, and if the DM doesn't like a rolled result, the DM rejects that result and either rolls again or just picks something. Even in AD&D, a DM shouldn't feel as though he's, like, cheating by rerolling or even picking what's best for that campaign instead of inserting something the DM knows is bad for campaign.
Thus, while the dice might've dictated that a ring of three wishes is somewhere in the dungeon, that doesn't mean the DM then must put it there or else the DM's doing it wrong. In fact, I suspect that Gygax would likely put forth that DM is doing his players a favor by excluding from the 2nd-level dungeon a ring of three wishes: a treasure like that at low levels skews players' expectations, giving them less to look forward to at higher levels when such treasures can be rightfully earned instead of accidentally rolled.
The Monster Manual (1978) in its description of treasure type further explains that the monster's treasure type entry means that such
treasures are only found in the lairs of monsters[, and] it must be stated that treasure types are based upon the occurrence of a mean number of monsters as indicated by the number appearing and adjustments detailed in the explanatory material particular to the monster in question. Adjustment downwards should always be made for instances where a few monsters are encountered. Similarly, a minor adjustment upwards might be called for if the actual number of monsters encountered is greatly in excess of the mean. The use of treasure type to determine the treasure guarded by a creature in a dungeon is not generally recommended. (5)
So this means the level 1 PCs upon defeating the 1–4 giant ants (see the DMG's Dungeon Random Monster Tables for Monster Level 1 on 175) should not get all or even the bulk of the giant ants' Q×3 and S treasure types but, instead, only a tiny portion—if any!—of that treasure, the Number Appearing entry of giant ants being 1–100, and even that tiny portion of giant anty treasure assuming the PCs defeat the giant ants in their (probably less than expansive) lair.
(If the DM doesn't mind mixing his dnd-bx material with his AD&D material, this DM recommends the Monster & Treasure Assortment: Sets One–Three: Levels One–Nine (1980) for a multitude of examples of reasonable lower-level treasures suitable for a party that's defeated, for example, some not-in-their-lair, less-than-the-listed-mean wandering monsters. The tables, if so desired, can also be used pretty much as-is, needing hardly any conversion.)
…But I understand wanting to roll dice and stick with the results
So you rolled a ring of three wishes and feel like, because it was rolled, it should be in the dungeon, darn it! That's cool. Make the ring almost inaccessible, nearly impossible to find except through great ingenuity, skill, or luck (maybe the ring's surrounded by puzzles and traps as the dungeon's centerpiece or made of glass and at the bottom of an underground lake). Or, perhaps even better, somewhere in the dungeon there's a clue that leads to another dungeon where the ring can be found. Or you can just give the PCs such a ring and see what happens; remember, these are AD&D wishes, after all.
Trip would go from cheap to worthless
The long-term issue would be diminishing the value of tripping. At low levels, PC's have precious few resources, so making trip less valuable means that it will see less play. That riding dog is a threat in its own right at 2nd level, but it cost some of the bard's gold. By even 6th level, the same dog is nearly useless; it's relatively fragile, and it's relatively weak.
Recommended Solution
I suggest mirroring how the Withdraw action changes merely leaving a threatened space. Thus it could be named Defensive Stand, or whatever, and be a full-round action, unless the creature is limited to a standard action (as with withdrawl, a nauseated creature couldn't perform this action) to stand without provoking Attacks of Opportunity.
This way any creature can take a move-action to stand, risking an Attack of Opportunity, but by taking a Full-Round action to stand, being properly cautious, they provoke no Attack of Opportunity. That way trip retains most of its value for wasting actions, and some creatures (low-no intelligence, or very aggressive ones) will still stand faster and provoke the attacks.
Best Answer
Yes, of course, removing a problematic element from the game is one of the reasons to have a DM in the first place.
But I have a hard time seeing how rod of force is that item. They’re extremely expensive (worth almost everything an 11th-level character owns, and not being realistically affordable until 15th or 16th level—and that’s just for one!), can only be used five times per day, and it functions as either a mediocre weapon, a mediocre blast attack, or wall of force, which is almost-certainly the best way to use it but I have hard time seeing how that could ruin a game. They’re fairly decent I suppose, with that flexibility, but I just don’t see how they end up being game-breaking.
For rod of force to cause so much trouble, I have to imagine that this character has vastly more wealth than the books would otherwise suggest. With that much wealth, they could be getting far more dangerous things than the rod of force. I suggest your review the wealth by level guidelines in the Dungeon Master’s Guide, unless you’re playing in the 15th+ level range—at which point, I would suggest your encounters need to be tougher if the rod of force is causing considerable problems for the players’ encounters. On a personal note, I generally feel that the game breaks apart on its own somewhere around 15th level, without any need for particular player shenanigans. I would thus suggest avoiding games that go so high, the system doesn’t work well when you do.