Well, for one, don't bother reading up. They will hire you even if you know nothing, they have such a high staff turnover that they don't care anymore.
All you need to be is a good salesman, as you will be working on commission and selling and promoting Hagen products.
I'd check into applying at a mom-and-pop type shop if you really want to care for and learn about herps. There are many good ones around. Sadly, the big chain stores are all about $$$.