You've done the right thing by coming here and trying to educate yourself. I wish more people would do the same before becoming pet owners.
Why rely on part-time retail sales people to be able to teach you everything you need to know about an animal that's going to rely on you for its care? Some can, and they are to be treasured - the rest may only know the basics. Don't learn the hard way which are which (and don't think for a second it has much to do with what store they work in - both kinds are found in big boxes and mom & pops alike).