Don’t know if this has been mentioned but in the event it hasn’t, another form of research is to get the vehicle’s service history. Just about any MB dealer should be able to get this for you if you provide them with the VIN. In addition, you might send email to Benzmac, MBStars, Steve and perhaps other techs here to get an informal (and I emphasize informal) opinion. Lastly, take the car to another dealer for a second opinion.
Hope this helps….