I agree with the doc on all issues noted here. Used to do Jaguar and VW OHC adjustments and taking cams out and back in, sometimes twice, is no Saturday party under a tree. To the guy in Finland, US version 8V engines are hydraulic autoadjusters, so valve noise is a larger issue than adjustment.
If your local guy doesn't have MB tools and serious training, the road to fining the problem can be long and expensive. European system philosophies, combined with MB's almost isolated approach to vehicle systems offers problems to the average technician that are not easily solved, even with the right manuals. If you don't have a serious indepenent shop, pay the fees for dealer service. It will likely save your sanity in the long run.