I don't know where you're getting your BP, but if you're planning on hitting up Twin Cities Reptiles(I don't know where else you'd go to get reptiles anywhere near Elk River) I'd trust them 100% on selling a correctly sexed snake, despite the fact that Hawiianice is pretty much correct in saying that most local pet shops don't know the difference.

That's where I got my little girl and they were a pretty big help.