Follow the instructions on these two links to flash to JH3. The fist link is for JH2, but the directions still work. Just download the JH3 firmware.
This page has all the files you need:
You need the firmware file, the PIT file, and Odin. The links for all of that is on the above page. The PIT file and Odin are under the section called "Flash Tools."
Once you've restored & upgraded, you can root or whatever you like. I'm a fan of SuperRooterExtreme, which does a whole bunch of things for you in one package.