The interesting thing about MarkC's is that you can go and talk to the techs about what they do to shop a machine, and you can watch them in action. I saw part of a process where the playfield had been 'nifti'ed, and the tech was working on buffing it with Novus and a sheepskin buffing pad on an electric drill (this playfield had a fair bit of ball swirl from memory). They also had buffed up the metal posts on a wire wheel or similar.
To what extent the machine gets 'shopped' will depend on your budget, but as a minimum I would expect replacement rubbers, playfield buffed and waxed, and any faults fixed (these would need to be in addition to a flat fee). If plastics are readily available you can request these are replaced at the same time. And the display as well, if it was tired.
