S3, 4.3? That's a big risk right there. Take the battery out and leave the phone untouched until you can OTA 4.3.2. Who knows what rooting that installation of 4.3 will do? I can almost (not definitely, but almost) guarantee that the phone won't blow up or catch fire. But bricking? Losing wifi? I can't count the number of bugs I've seen on Android Forums alone for the S3 4.3 combination. I would be leery of dialing a number on that phone.