What you're gonna have to do is flash the firmware using RSD Lite.
First You'll need too download the firmware: http://sbf.droid-developers.org/phone.php?device=8
download your version and build.
While you're waiting for that to download, download this https://dl.dropboxusercontent.com/u/...ite_v6.1.x.zip
when its done unzip it. And install RSD Lite 6.1.5
Now when installing rsd lite itll stop and say it cant go on. Don't close the installer. Go to the file directory where rsd lite will be at witch should be in on the the programs folders. Once you find it make a new folder in the Program Files (x86) and make a folder called RSD Lite. Move the files to that folder then close the folder. Then you can make a shortcut and use RSD Lite.
Now when your firmware is done downloading unzip it. Next go into the folder and find the .xml file and open it with notepad.
What you're gonna do is delete most of the lines it should look like this:
<phone_model model="SM_JB_VZW_1FF" />
<software_version version="smq_vzw-user 4.1.2 9.8.1Q-66 28 release-keysSM_BP_101031.027.32.81P" />
<interface name="AP" />
<step operation="flash" partition="logo" filename="logo.bin" MD5="506F42184C465D9CD8BB2BD27DB77F1A" />
Now put your phone in fastboot. and open up RSD Lite. Once rsd is open plug in your phone. click the button with three dots. Find the folder with your firmware and choose the .xml file and press start. Wait a couple seconds your phone will reboot when its done you're set. if somethong goes wrong let me know.
Hope this helps.