jlee if im not mistaken the only way to completely get rid of all things sprint, you would need to either build your own rom or use one of the rom's that are on these forums made by the geniuses on here. you will need to unlock you phone first for either suggestion.
go here for unlocking instructions.
http://forum.ppcgeeks.com/showthread.php?t=42503
definitely read ALOT first before attempting to flash anything as they can damage your phone. then once you feel ready go for it. and if you want to build your own go to ppckitchen.org and learn how to make your own.
it took me six months reading these forums for hours before i had the courage to unlock and build my own rom, but i am glad i did. i didnt have one hiccup during the whole process. good luck and as always SEARCH before you ask and then ask if you cant find the answer.