Sprint has never been into covering water damage. I had the Newton's Rings on my screen...they looked at it for about 5 seconds and ordered me a replacement. No fee and no questions beyond that asked.
The tech did give me grief for "junking up my phone with that Apple Slide 2 Unlock crap" though. Apparently he was as Anti-Apple products as I am!
Do you have TEP? If so...then you more or less have absolutely nothing to worry about! Most of us will agree that you shouldn't be too worried...Sprint will get you taken care of...they can't afford not to!