this guy wants to sell me a 1993 s 500 mercedes in fair condition for $3500 cash the transmission was rebuilt a month ago. the engine has a little tapping thats what concerns me. its not nocking and it has a lot of power the speed tac says 130000 but i think it ma have stop working. the interior is fair the exterior is in good condition should i buy it. or turn my back and run like hell thanks for the help.