Peter Vanderveer (Vanderveer Motors) in Norwood, MA is excellent. While his shop is modest (looks like a barn) he is very knowledgeable about both diesel and gas MBs of all vintages. He is willing to take the time to discuss and explain problems and solutions so that customers understand them, and if a part can be reliably repaired, he will repair it rather than hit you up for a new replacement. I have seen him disassemble and repair heater valves, window switches, etc, when new parts were unavailable or very expensive. When you get your car back after repairs, it "stays fixed"; you don't have to go back three times before the problem is corrected. He is not cheap, but he's less costly than an MB dealer and much better than the vast majority of them. Try him if you're in the Boston area.