Such player devices enable owners who do not actually play, themselves, to put wear on a piano far in excess of what might otherwise be expected of a 19-year-old instrument.
Plus what all the others said, above.
We have no clue where you are, so the only way to help further is to suggest http://ptg.org
,who may be able to recommend a technician near where the candidate piano is. That, or you might try some long-distance telephone detective work. Possibly, calling the Steinway dealership that serves the location for a referral.
Oh, and what did you mean by, "seller appears to be honest armature individual?" I know autofill or autocorrect can do some wacky things, but...
Anyway, good luck with this one.