For those of you who want to try the latest Android 4.4.2 + Root for your AT&T Samsung Galaxy S3 with model number SGH-i747, you do not have to unroot and go through a lengthy process.
Our recommended method to install the Android 4.4.2 + Root via CWM or TWRP recovery. This is fully-stock, 100% same as stock firmware but with root.
For those of you with an older bootloader (You’ve rooted your phone on 4.2.2 or earlier), you will need to flash KToonsez kernel to make it boot.
If you already have Android 4.3 bootloader or later, you can just flash the ROM and should boot fine. Also, if coming from stock rooted ROM, you may be able to install without doing a factory reset. Just make a backup ROM and install ROM without factory reset if that’s the case.