It depends on the actual Sprint store.
I've ran into a couple that did "instore repair" that for whatever reason never charged me to replace cracked screens.
I remember one in north Houston that was churning them out for every customer that was coming in there as long as they had the TEP.
That same store once replaced the screen 3 times trying to get it to work right without good results, so they gave me a "refurb" for no charge whatsoever. Hell, I even asked a couple of times - how much was this going to cost me and they kept insisting that as long as I had the "insurance" I was solid.
Again those stores are hard to find.