Jim Battle wrote:
 With a sinking stomach, I unscrewed the case to find inside...
 a sheet of 1/2" plywood screwed to the bottom, with no main board.
 I'm guessing somebody "tricked out" the case and was using it
 simply as a keyboard to some other project they had.
 I emailed back to the seller, and his position was more or less that
 he had told me about the lack of connectors (the power, at least). 
This sounds like a good candidate for the Ebay Insurance program. Missing
connectors is not quite the same as a missing mainboard. It doesn't sound
like intentional fraud, but I would most certainly follow up with Ebay.