Check that the head functions correctly, I had problems with mine, the relay board which controls the head movement needed reflowing of solder on the relay and header pins. Apparently this is a common problem.
I believe some of these machines were shipped with 'diamond plate' play fields, that would be a good find.
My machine came with mylar which was quite worn but the play field looked great once I got the mylar off and cleaned up the rest, but it did have some wear down the outlanes. Nice game, I enjoyed it while I had it.