Put on any plates. A cop is not going to scan your plates for no reason. Drive smart and you will be fine. If I were you, I wouldn't even take the car to the mechanic. Drive the vehicle and make sure it drives nice, shifts nice, and no weird noises. Give it a few full throttle rips that will tell alot. If all that is ok, then the car is fine. You can tell alot about the way the car was treated just by the condition of the exterior and interior. The mechanic is going to ask you "what do you want me to do" aka how far are you willing to open your wallet? Waste of time in my opinion if your taking it to the mechanics to have it checked. Unless of course he is your friend and will do it for free. What are the details of the car? Make, km, year?