ok I don't really know much about how to do any of this stuff but I will tell you what I have done to my phone so far and hopefully someone can tell me step by step what to do in really simple terms.
I have v2 of 2.1 on my phone and it is the version that roots your phone too. I want to unroot my phone and make it stock again but I don't know if I am supposed to delete the file from my phone which had 2.1 v2 on it or if I just leave it on there.
Though I am not quite sure what you are talking about when you say, "I have v2 of 2.1 on my phone and it is the version that roots your phone too," you can do either delete it or keep it - the file itself is not what keeps your phone rooted. As far as I know, you will keep your SD card with the phone that Verizon replaces for you.
I have the instructions from xda forums "Charge your phone's battery completely, put it on a charger, boot to Amon_RA, Wipe, and then flash the "FlashBack15_v1.zip" ROM." The things I don't understand are boot to Amon_RA, wipe, and then flash the ROM.
Can someone explain these instructions to me in very simple english to me?
Hopefully charging completely and putting it on a charger is self-explanatory.
Boot to Amon_RA - this means that you turn off your phone and boot to Amon's recovery so that you can flash a new ROM - the Flashback1.5 ROM. You boot to Amon's Recovery by holding down the Vol Up key while you power up the phone until you see a screen with green text on a black background. That's Amon's Recovery.
Wipe - while within Amon's recovery, use the trackball to roll down the highlight to the "wipe" menu, then press the trackball to select that. From the screen that pops up, press the trackball on the Factory reset/data wipe option. When that it complete, press Vol Dn to go back up to the main menu. Before doing this, however, I would suggest going to the Nandroid backup menu item and running a nandroid backup of the phone, so that you can recover your phone to where it is now in case something messes up. After running the backup, go back to the main menu with Vol Dn and then do the wipe procedure.
flash the "FlashBack15_v1.zip" - Hopefully you have already copied this file to the root directory of your SD card (and, just to be clear, this is not a directory on your SD card called "root" - it is the top directory of your SD card; i.e., do not put this file into a folder on the SD Card.) Obviously, you should have done this before turning off your phone and starting in Amon's Recovery. Anyway, from Amon's main menu there is an option to flash a zip file from the SD card. Roll down to that menu option, press the trackball. That should bring you to another screen, from where you can roll down to select the "FlashBack15_v1.zip" file, press the trackball, wait for the phone to finish. When it does, it will return to the main menu, from where you can press the trackball on the restart phone menu item.