I agree that when you talk to the salesman about this vehicle it's best to have as much technical knowledge as possible. I've found that most of the salesmen at MB dealerships don't know much about the older models, especially the technical details.

That reminds me of an S320 that I took for a test drive with a salesman. The following conversation took place:

Me: "Do you happen to know if the wiring harness has been replaced? I know that was an issue on the W140 models."

Salesman: "But this is an S320."

Me: "An S320 is a W140."

Salesman: (Confused look.)