With a 97 840, the engine is the least of your worries - thus a mechanic is not the priority. Take the car to a great body shop where they can tell you for sure if the car has ever been hit or painted anywhere. When I bought my 97 840 from the dealer, I had them sign a letter guaranteeing that the car had never been hit or painted. You'll be amazed at what dealers will sign off on when their commission is at stake. The Carfax is good, but far from perfect.