First of all you will need your cpu key, which you can get by booting your jtag with the eject button. then your need to dump your nand using flash 360.( i dont knw if i can post links here but for the mean time just google it) and download it. also download xebuild latest one. here's a video to walk you through it
This is my first ever tutorial i knw it sucks. but if you have any problems let me know.