Aside from the obvious purpose of returning a defective unit to Verizon, this stock package can help you to discover whether a bug they encounter is specific to whatever custom ROM you're on or if it's a stock issue as well. Also, if you encounter serious problems while flashing a custom ROM or other mod, it's like a easy-to-use panic button to get your phones back to a fully-functional stable state to start over with.
The instructions for flashing this are as follows (assuming you had already followed the instructions for rooting your phone to begin with, such as installing the USB drivers, etc.):
- Download the Odin package posted in imnuts' thread
- Put your phone into download mode and connect it to your computer
- Open Odin and make sure your phone is selected
- Put the downloaded file in the PDA box
- Press start