If you havent already. then read this
http://forum.ppcgeeks.com/showthread.php?t=20370
it'll get you started. Then find a ROM specfic to your carrier (Verizion,Alltel,Sprint) then read,read,read. and if your still fuzzy ask more questions, specific questions so it'll be eaiser to get a good solid answer. Theres always people here willing to help. And remember to SEARCH! Most questions you have, Have probably already been asked and answered.
Have fun!