The easiest way would be to stack Chameleon spells and effects (via Alchemy, enchanted items, or a custom spell), until you have a total chameleon value of 100% or more. With 100% Chameleon, you can basically do whatever you want with impunity, as nobody can see you, and unlike invisibility, Chameleon does not break when you interact with the world around you.
See also: UESP Wiki on Chameleon in Morrowind
In order to gain a level in Morrowind, you must improve your Major and Minor skills by a combined 10 levels. You can gain 1 level in each skill, or 10 levels in one skill, or any combination thereof.
Afterwards, you need to sleep (not just rest/wait, but sleep, either in a bed or in the wilderness), and you will be able to gain a level.
When gaining a level, bonuses will appear, up to +5, for your different attributes, depending on the skills you leveled up since your last level. This includes skills that are neither major nor minor skills. Therefore, increasing these other skills can be a good way to ensure you get a +5 in the stats most important to you. The bonus is defined by the attribute associated with the skill, so therefore, Luck will never get a modifier.
You pick 3 attributes to increase at levelup, so if you have bonuses on 4 or more attributes, extra bonuses will be lost.
It's also important to note that, if you gain more than 10 major/minor skills before you get a chance to sleep, the extras will carry over towards counting for your next level. You will only gain one level for each time you sleep, so if you've gained 20 or more skills, you'll need to sleep at least twice to gain all your levels.
Any attribute bonuses you've accrued go away as soon as you've gained a level, so it's generally preferable to level as soon as you get the 10th skill, or else you're liable to waste attribute bonuses you could have used otherwise.
Best Answer
You might check and see if you can't just rebind the key in the options menu. Many games support both keyboard and mouse input, and I seem to remember that you can rebind most actions from mouse buttons to keys, although selecting dialog options (and the like) might be always mapped to the mouse.
If the game makes you use the mouse, AutoHotKey is my go-to solution for these problems. It's free, and it downloads and installs quickly, and it works with games in many cases.
In this case, you might be able to get away with:
which would map your a key to send the left mouse button, and your b key to send the right mouse button. You can replace 'a' and 'b' with whatever keys you want. Some keyboard keys have special names in AHK; there's a list of all the keys here.
Open a Notepad window, and copy and paste this line into the blank Notepad document. Save it as "mousebuttonremap.ahk" (including the quotes) and then you can double click to load it. There will be a little "A" icon in your tray that you can right click to quit the script, when you need your keys back.
Sometimes this method doesn't work with games, in which case you may want to try:
If this still doesn't work, you may have to tweak the script a bit more to work with the specific game you're trying to play. There's a FAQ entry about issues with games that might help in this case.
Update: According to other users on the AHK forums, SendEvent works best, and you may need to edit Morrowind.ini to set "Background Keyboard=1" for this to work properly.