Here is the problem right here. I wouldn't let a Best Buy tech anywhere near a car. I've never seen anything good result from it. Ever.
Seriously. Also, not to add to the pain in the ass this has created, but I'd be a bit leery of any hidden electrical work (no matter how basic) done by somebody that signs off on the sort of, er, craftsmanship that you
can see.
I agree with the suggestion to show him this in person. A phone call isn't going to cut it, plus dealing with situations like this in person can sometimes work out a bit better. It's harder to be an ******* in person than it is on the phone, basically.