Most Sprint stores will probably say no within the 14 days. During that period, you really should return to the point of purchase and exchange for a new. Only time this is a problem is when a phone launches, typically.
Otherwise, TEP covers the phone no matter where you got it. Or, $35 if you don't have insurance/s&r and it's repairable.
If you don't really need any special treatment and just want a good deal, Best Buy/Wirefly/etc. can be good options. If you are doing things right, you should just plug in a gmail address and it will pull your contacts, etc. Pretty much any smartphone can sync your current contacts to gmail (Blackberry, iOS, etc.) if you have a smartphone now.
But then again, Sprint will transfer numbers anytime for free. I'd imagine Best Buy has cellebrite machines to transfer numbers. Either will work if you have a feature phone right now. But...you could bluetooth them yourself and save a trip if you buy online.