Just call S&W. 1-800-331-0852
http://www.smith-wesson.com
I've had very good experiences with their knowledgeable staff.
Ifyou like the feel of the 910, you may want to get a catalog or ask about similar models you didn't see in the store. Some may have differing features and actions to suit your preference. Variations may include steel or alloy frames, fixed sights, adjustable sights, night sights, ambidextrous safties, decocker-only safeties, DAO vs DA/SA, gun size, different finishes, and grips.

They can also give you some history on used guns if you are ever considering buying one. Just get the model and serial numbers.

My old 39 is not rated for +P, but I think most of their newer models are.