I think it should be no more than $10-$12k if it's mint. These things only bring $8k or so on ebay. This may sound strange but don't worry about the dealership, worry about the car. If you are concerned and not very mechanically inclined to these cars, spend $100 and get it checked out by an MB tech. Run a carfax, see if there is any paint or body work on the car, etc. IMO, you will like the 300SDL better and for less money.