Disklavier

Hi-

I have a chance to purchase an early '90's vintage disklavier
upright for under $7,000.  According to the owner, it is a
one owner piano in excellent condition.  I know that, in addition
to checking out the original bill-of-sale, that I can submit the
serial number to Yamaha for verification that it was made for 
the US market, and that it was sold to the current owner.

What else do I need to be careful of?  Any thoughts or opinions?  

Thanks.

Gary Schaps