I know of a couple, and there is a thread somewhere in the Shops forum on DC. Mitch Carr in Kensington, MD I found to be very honest and reasonable, but he's very, very busy. So I had to set up an appointment and actually left my car there while on vacation to get a number of things taken care of.

Another one I have used and thought was fine was A&R in Merrifield. They're in the Texaco station at the corner of Rt. 29 and Prosperity Ave., right near the big post office.

I was not as happy with the MB independent across the street, as everything they did (when I first got my 300SD) had to be redone sooner than I would have expected. They also told me they couldn't figure out why my oil pressure gauge didn't work, but I asked the question here on the Forum and it was a 5 minute diagnosis and I replaced the sender unit and voila! It was fixed.

__________________
1987 300SDL 265,000 mi.
1982 300SD 325,000 mi. (and holding)
1956 Packard Clipper 150,000 mi.