I'd suggest just browsing through the ROM hacking area that we have here. There are a looot of tutorials, there to go off of. Also a fair amount of help threads, and members who know a lot about ROM hacking, who are glad to help you out.
Sooo, head over there and you should find what you need.
Good luck with your hack, but this area is for intro threads, not question threads.. soo I'm gonna have to close this up. D: