Hey Everyone - I got my X5 back from the Mercedes indy that did the work. Unfortunately, I can't give you a specific amount charged for the work b/c I also had the ball joints done on a e430 4matic that I own. Now, I paid $40 for the BMW CV Boot Kit (from the dealer) and the guy charged me $340 labor for both the cv boot and ball joint repair (I purchased the ball joints separately from the mercedes dealer).

So, a the total cost for labor was $340. Now, the mercedes indy did tell me the cv boot job was not easy and he did pull the axle out (I wasn't there so I'll have to take his word for it). But considering the BMW indy wanted $600 just for the cv boot job, I guess I'm way ahead of the game. Thanks to everyone who helped me out with all the info in this thread.