I wouldn't let anyone but the dealer do it if you want the motor to remain intact for very long after the service is performed.
the price they are quoting you should be to replace all the tenson and idler pulleys as well as the belt and the water pump. if you don't have a complete service done your asking for trouble. I also seem to remeber that the nose of the car has to come off as well....
fly by night die by night
I would personally rahter have someone who works on audi's all day long and nothing else do the work If I wasn't going to do it myself...