I looked at doing this but you need to change everything, the runners/frame for the windows, the switchgear front drivers side & back and the full wiring loom, new rear door cards (or blanks for the winders) and the plastic inserts for the rear switches and the drivers door plus obviously the motors.
Nothing is prewired on the manual windows. It can be done but seriously not worth it.
The trim just clips off, so if you've got plastic walnut definately worth doing, you could sell the old trim on ebay as well as for some reason there are still plenty of people who seem to think fake wood looks good in an Audi.