As the topic says, has this been done?
Yes, you must get soff first. I would try firewater first as it is free, but if that doesn't work, you can try sunshine, and it will let you know if it will work, just not sure if it works on gpe.
After soff, you change your cid and flash a sense ota firmware in RUU mode twice to correct partitions, make sure android text file in firmware.zip matches your MID and Cid, if not, just manually add them. Once you flash firmware, flash twrp or whatever recovery you prefer and format, then advanced wipe and wipe dalvik, cache, data, system, internal sd. This will wipe entire phone btw so backup first, load rom from your ext sdcard or push with "adb push rom.zip /sdcard/" and flash away. If you get an error on wipe, "unable to mount E: cache" just unselect cache as flashing the firmware probably wiped it. enjoy. Remember, MID and CID are very important!! Soff required, do not even try without it. You can find the ota firmwares pretty easily, just look in the rom sections.
One more option is to change your cid to at&t CWS__001 or Super 11111111 and change your mid to 0P6B12000 and just flash att 1.58 ruu floating around. You just put your phone in hboot mode and run exe. This will make your phone an at&t phone, then you are sense and can flash away. Pretty easy, plus that mid is supported on gpe conversion so you can just flash the gpe ruu to go back. SOFF still required for this!! I wouldn't think this would sim lock your phone, but have never tested it.. just saying
