There's been a massive amount of changes. Obviously there are new zones, new battlegrounds, higher level cap, new skills, etc, but I'll try to cover the biggest changes as they will probably affect your character:
- Two new classes, Death Knights and Monks.
- New professions, including Inscription which affects every character through the addition of glyphs to modify your own talents and spells.
- Completely redone talents: there are now only 3 talents to pick from for each tier (and there is a tier every 15 levels). This was instituted because a staggeringly high number of talent trees had almost identical builds. These new talents represent the minor variations from the stock builds.
- Specialization (BM vs MM vs Survival) is now separated out from your talents. There are no longer "BM" talents or "MM" talents.
- Removal of many statistics from items, e.g. attack power, spell power, and the addition of "mastery".
- The Dungeon Finder makes running dungeons infinitely easier for DPS, as it is really quite easy to get pick-up groups compared to vanilla and TBC.
- New raid difficulties:
- LFR - dungeon finder, but for raids!
- Flex - anywhere from 10 to 25 man raids. Bosses scale to howevery many you have. No more waiting for 2 more DPS - it just scales back the boss to make it a fair fight.
- Heroic 10 and 25 (tougher bosses, better loot)
- Badges of Justice/Valor replaced with Justice Points and Valor Points. Valor points mainly used for upgrading gear. For example, a 528 LFR piece can be upgraded to a 532 for 250 valor points, and again to 536 for 250 more.
- The ability to raid in pick-up groups quite successfully in each tier.
- Achievements.
- Hunter specific:
- No ammo (speaking as a fellow Hunter)!
- No more "Bow Slot" (librums, totems, idols, wands). Bows and wands are now actual Main Hand weapons. So no more agil-staffs or polearms for Hunters!
- Hunters use focus now, very similar to rogues energy.
In terms of classes, trying to cover all three roles between the two of you is a good target. When you guys are questing together by yourselves, having one person be DPS and the other healing helps keeps downtime to a minimum. And if you guys decide to use the Dungeon Finder, having one person able to heal and the other be able to tank ensures you'll never have to wait long in the queue.
Blizzard has homogenized the classes over the years so there is a tremendous amount of overlap between the classes and specs. As long as you guys cover the three class roles, feel free to choose whatever fancies you.
For reference the hybrid classes are:
- All three roles: Paladins, Druids
- DPS + Healing: Priests, Shamen
- DPS + Tanking: Warriors, Death Knights
If you're going to take my advice about role coverage, you'll want to avoid Mages, Hunters, Warlocks, and Rogues as they can only be one role: DPS.
Since you're talking 1-85 play, Death Knights are off the table as they start at level 55.
Putting it all together:
- Person 1: Paladin, Druid, or Warrior (to cover tanking)
- Person 2: Paladin, Druid, Priest, or Shaman (to cover healing)
In terms of professions, I'd avoid the heavy crafting professions that take a lot of time to level up and are usually taken for the Bind-on-pickup endgame recipes: Blacksmithing, Tailoring, Engineering, Leatherworking. Instead, focus on the professions that'll let you help each other out while leveling, like Enchanting and Alchemy, or the gathering professions, like Mining and Skinning, which will prove lucrative and won't require too much (if any) time soloing.
Best Answer
It's worth noting before we start that World of Warcraft is a region locked game. It is available in a variety of regions (EU, US, TW, KR) but if you purchase a copy for another region it will not be compatible with all regions. If your friend is to be playing with his American friends, you will need the US copy if they play on the US servers
According to the various Blizzard sources, in order to gift a copy of World of Warcraft or one of its expansions to a friend you do the following;
In order to play the whole of World of Warcraft (ie: get to level 90, explore all of the zones, etc) you will need to purchase all of the expansion packs - only buying the base game will still provide a large amount of content to play, but will prevent your friend from playing any of the maximum level content (or indeed, some of the content before that such as Cataclysm content).
If you need any further assistance with this, or "official" help, I would recommend contacting Blizzard directly.