I am writing this because I had to do it. I hosed my phone and could not get it to boot into OS. I did get it to boot into recovery, and fast boot. This will work if you can get that far!
1. Download the stock ROM ZIP image from here:
Sprint Stock ROM Image v 1.1.3.651.7
2. Copy it to SD Card. You may need to use a card reader if your phone is hosed and wont boot to OS.
3. Reboot phone into hboot mode by holding volume down and then press power. Keep volume down held until you boot into hboot mode.
4. In hboot mode the phone will scan the SD card with the image. Once it finds it will ask you if you want to update. Press "Power" to update.
5. Wait.... For a while. When it gets to "system" it will loop a few times. Its quite nerve wracking actually but after about 5 or 6 times it will complete.
6. Once the entire flash is complete it will prompt you to "press power to reboot." Press power and your phone will reboot to 100% stock ROM.
7. Once the phone has been flashed you will need to set the secure flag on the radio for S-ON to do this use "fastboot oem writesecureflag 3" Make sure you are in fastboot menu. To do this power down and hold power down while powering up and select fastboot. I attached fastboot and ADB to the post if you don't already have them.
This has only been tested with TeamWin recovery and phone was already at the v 1.13.651.7