This is a long shot...but I grew up in Needham and one of the older Boy Scouts in my troop was a VERY good mechanic. When I moved from the east coast in 1988 he had already opened a shop. I Googled his name and came up with the phone number below, I assume it is the same guy I knew, how many Rusty Whittakers can there be in Needham? I don't know if he works on Mercedes but I would trust him unconditionally regardless. He is an outstanding person and mechanic, and he sparked my interest in things mechanical (pun intended) though since then I've lost interest in the spark
Whittaker Automotive (Rusty Whittaker)
Needham, MA
781-444-3703
Tell him tall, skinny Chuck sent you, and that I wish I still had the Can-Am 125 dirt bike I bought from him back in 1983!