The low down:
I would check for a history of service with the books that come with the car first. IF not there, call the dealer. IF you do have history, still call the dealer and confirm!
Check in the valve cover (under the oil cap) for dark brown or black residue. In a Mercedes Engine with less than 100k miles, it should be a light silver if the oil was changed regularly.
Drive the car and see what you think.
If there are any problems like the wirring harness, the dealer should do this under a "good will warranty repair" Our local dealer RBM of Atlanta has done at least 100 or more for us. They say it has to be under 120k miles.
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