okay i think i can help you BUT...im assuming you have a modded box? if not start there then come back. if you are modded then...
1. Get the Halo Cache Editor from xbins or PM XboxWar3z about being a beta tester for v.08
2.go to halomods.com and download what ever mods you want and put them in the PPF folder of your region.
3.Load up desired level in halo,reset, open the cache editor,press select the go to patch cache file,patch and play.
if you for some retarded reason dont want or cant find the cache editor then drop me an email at
[email protected] and ill explain the hard way to do shit.
oh yea i for got about the modding it yourself..
if you want to make mods go to halomods.com and look in the utilities section and download HMTv3.5 and sparkedit 3.something
then search through the forums and all will be made clear as mud