sorry mate i cant help ya, but i know what your going through, i tried to mod my old psx and it fried the ****er...probably cos ive never used a welder before #-o
your best bet would probably be getting some advice from some modding forums, theres heaps around. and ive heard the xbox is not particularly hard to chip, a guy i used to know put the 40 gig HD in one in about 2-3 hrs, so its not complex but you gotta know exactly what you are doing.