Check all the boards in the backbox to look for bad hacks and ghetto engineering repairs especially on the power driver board.
Ramps have been repro'd as have been the faces so you can always replace those if broken/cracked. Check the head motor and everything in the test menu to make sure that is working.
Obvious things like playfield wear, only a very small # of that game had diamonplated playfields but most had factory mylar. Sadly no one has repro'd the playfield yet but I'm sure hoping someone does someday before I die so my game can be as mint as the rest of my collection.