Have them fix the badging, then question the owner on the mileage discrepancy. If your question isn't answered to your liking, inform them that you were planning on having them work on other vehicles in your stable and would now shop around. Also inform them that you will be discussing the issue with your attorney, then leave.

Have your mechanic check the vehicle out to make sure that nothing is wrong with it.

Don't bother talking to a lawyer, there's no proof, other than your word, that you zero'd out the tripometer. You also claimed that you had no fuel when you dropped it off, but now have half a tank. they probably didn't charge you for the added expense of the fuel.

Just walk away and vow to never do business with them again.

__________________
1987 560SL
85,000 miles