The power supply is an internal one, that's how I was able to figure out the colours of the wires on the connector that would have plugged in to it and then guess as to what they may be.
I've already googled the model number of the set, which is how I was able to get the part number for the power supply. Pretty much every place I've found it listed says that it's out of stock or discontinued.
I found one on Ebay for $49, but like you said about its condition and the fact that someone else gave up on it, I don't want to spend that kind of money only to find out it's dead.
Given that the power supply is a discontinued item, I am hoping that whoever had it previously determined it was the power supply that was bad, couldn't find a replacement and then threw it out sans power supply and back panel.
If it does indeed turn out to be dead, then it'll just get cannibalized for components
