That's great!
Just from a customer's perspective:
My biggest piece of advice, if a customer asks you a question, don't bullguano them. If you don't know, tell them you aren't sure but would be happy to find out for them (aaaand google) I normally play stupid in gun shops, ecspecially cabelas or scheels, just to see what comes out of their mouths. Sometimes I don't have to play dumb, they just voluntarily vomit ignorance. (see my post about the difference between .223 and 5.56)
Be prepared for the worst gun handlers in the world, safety wise. Anyone who teaches CHP classes may be able to give you some tips on how to deal with that.
Talk to Dave or Thomas about how to help people select a pistol for fit. It's important, and most people have no idea how. I could give you a rough picture, but Dave or Thomas could go into much better detail and experience.