I'll try to keep this short because I sometimes go off into tangents lol
I don't think you overpaid by too much. If it was a proven genetic granite LB, $500 is pretty cheap for a 3 banger. Since it's not a granite though, I think you only overpaid by a relatively small amount. However, if you're happy with her, you could just eat the ~$60 you overpaid, and consider it a lesson learned. That's what I would do, simply because I'd rather not start getting tangled with a huge BOI war with someone with a bad reputation. What have they got to lose? Bad customer service, constant mislabeling of morphs, selling hets that aren't really hets... It doesn't seem worth it to me. I know some people have the energy to go after them and get what you want, but I think all you're going to get is more stress and a headache from not getting what you really want from them..
I don't think you're a moron, but you've been out of the hobby for a while, so you just have to slowly get your legs underneath you before venturing out and buying morphs. The Desert morph is a hot one, but don't go buying a female in hopes of breeding, because they can't lay eggs... It's easy for someone who doesn't know these things to find themselves in a similar position as you are.
As for the refund problem, I already stated what I believe, and I am sticking firmly with it. If you're offered a refund, and you choose to accept it, it's a done deal. Refund is owed, no ifs or buts... I think it's pretty straight forward.