I drive a 1991 318is. I have noticed what appears to be belt noise coming from underneath the hood. Since the car recently turned 100K miles, I figure its time to replace all the belts and start fresh. My questions are as follows: (1) How many belts will need replacement? (2) Since I am replacing all the belts, what can I expect to spend in parts (ballpark estimate)? (3) Is this a job that can be done relatively easily or am I going to need special tools; and (4) If I decide to have the work done by an independent BMW mechanic (i.e. non-dealer) what is a reasonable price for parts and labor?