It took me years to come to this conclusion: When you have a Benz you had better be doing all the work yourself. Whenever I get my hands on a used one - and I can't afford new - I find that wherever mechanics have been, there are broken or missing parts or screws overtightened or not tightened or cross threaded. It never fails. And I have watched them: They will not clean an engine before they work on it and not repair/replace things that now are accessible because they have taken something off. (like the radiator). I bought a car that had "unrepairable" oil leaks. The previous owner had it at two repair places and it still leaked a lot. He sold it, to end his problems. I found - after spending a lot of time - a loose screw. It looked ok, but wasn't. I really hate to remove that transmission, I really do. But I'm convinced that the shop would screw up. Furthermore, I'm convinced that many other guys have had the same experience.