ALWAYS ask to see the part they are replacing and judge for yourself if it is worn. If you cannot get to see the part before the work is done, have them save it for you to look at when the repair is completed. One time I was told I needed a new Window Regulator (the thing that makes the window go up and down behind the door). When it was shown to me it did not come from my car, mine was electric, this one had a crank. The mechanic tried to charge me $400 as well. Needless to say, I brought it to the dealership owners attention. Not only was the guy fired, I got a shitload of incentives from them to keep my business. You know more about cars than you think, just about anyone can see something that is broken if they see a good part next to it.