I hate games that are a click fest or that try and shoehorn "mouse dexterity" into game dexterity. The interface in the game is really pretty good. If you get into a sword fight (not a good idead for most thieves, going up against armed guards) it's basically right or left click (for hack or for slash, I think ... didn't use the sword much)What you use more of is the bow or blackjack. The Blackjack (club for knocking out folks) is just a click and hold while you manuever closer, then release (*thud*).
The bow is a little more complex: click and hold to bring up the view portal (an area you are targeting, about the size of your thumb - or my thumb anyway ). If you hold long enough, the view portal zooms in a bit closer, for those long range shots. Then release the mouse, to fire. You can also you two keyboard keys (I forget which ones) to "lean" around corners, while firing.
Really, if you've got 2 or 3 working fingers and can operate the mouse (at solitaire level), the interface should not be a problem. There were a few run and jump (press space to jump) places, but not too difficult. And they have a save game feature, so you can always try the jumps again (even if you make it, just to see how you would have died })).
Tools for your Wizardry(r) toolkit