If there maps, go into the Halo CE files and put the map file into the file named "map" or something like that then, when you play halo it should work, but if its the menu or something you have to take out of the maps file, a file named "UI" take that out and put the one you got into it, but all the other mods are programs you just need to double click on em.
Go to www.MacGamingMods.com it will be There
you go and type on the internate how to mod halo combat evolve and then you download HTML
depends on what you're looking for. but most good mods in halo require a jtag. but a good site to look up mods is- http://www.thetechgame.com/
As of now the Halo: Reach beta is gone, your not going to be able to.
Mods.... search halo armour oblivion
You can in HALO 1 if you use mods, but it has to be on the computer.
Yes. There are a lot of mods for Halo and Halo Trail on PC.
See halomaps.org for mods like sonic for halo. It is only for Halo Custom Edition, but you can convert it to Trial or Retail with Pearl or Demo with Queene Anne's Revenge.
Yes
No, not without mods.
Not without using mods.
Aimbots do not exist for Halo 3. There are mods for maps though. If you put mods on your file share, it is possible you will be banned though.