My S3 stopped working immediately after connecting a USB camera

After searching the Internet I believe I blew out the chip that regulates the Power in and out of the phone. My question is .... is my only hope of recovering data from the internal memory to repair the motherboard by replacing the power chip?

If you can do chip-level repairs yourself, probably. A repair shop, though, won't - they'll replace the motherboard. (Some specialized ones do, but most of them don't even have the equipment to.)