I would not recoment using red bulbs, I have red bulbs and well it not good during night.
however its easy, which bulbs are you talking about, the ones that are in like tach and sepedo. then just easily unscrew the wheel cover, two sqrews undernesath, then other two screws that are holding the dash. then the hard part, take the dash out enough that you be able to unplug it from behind. then just unscrew one bulb and screw another in.
But, what for red bulbs? Audi has benn using red ilumination of tacho, speedometer, heater, etc in all models since 1983, at least in Europe . Unless US versions don't have it?