I contacted the seller of the panel and he said it was indeed a used panel. That begs the question as to why it was so expensive but anyway, the situation was amicably resolved and I got my money refunded. I'd buy from him again, since he seems a straight, honest dealer.
Yesterday on my trip to Harbor Freight, I got a couple of things including a 15W solar panel. Now that panel turns out to be much heavier than my faulty panel. Checking the screw holes, they're a bit big for an 8-24 and a bit small for a 1/4-20. I'll have to find something that fits. That's a trip to the hardware store.
As the panel will be supported by solely 4 bolts and the 14 gauge bus skin is quite thin, I need to spread the weight a bit. This means I'll probably end up with two steel strips with bolts welded to them, one for each side of the panel then rivet the strips to the bodywork. I can then fasten the panel with lock nuts.
I posted a photo of the problem areas of the solar panel online. Apparently it looks quite shot. The seller just refunded me and said he didn't want the panel back, that means I now have spare cable and connectors, which is very welcome.