Call your local dealer and get them to fax a list of what they would do for the 120,000 mile tune-up; that's what I did for my 1992 500E...pretty much every fluid should be changed as well as the normal plugs/wires etc. I can send you my copy too as I think most newer MB gas vehicles will have the same items on the checklist. As for pulling the motor apart to do chain rails and timing chain, valves, etc. that depends on the condition and performance of your car. Hope this helps although I'm pretty much a DIYer. Try hailing Italianbenz or Benzmac for a true professionals opinion. Good luck.
1992 500E 128,000 miles strong