Welcome to GC. We have some members who are good with electrical. They should be able to give you some guidance.
Agreed. You could probably part it out and get your money back if you had to.I don't have any helpful info for you other than it may take some time digging through the wiring to find the problem. But at $600, I think I'd be willing to take a chance on that bike if that is the only known issue and the rest of the bike looks good.