head on over to halomods.com and check under files for some tools so u can do this stuff that u want to do they should also have tutorials on there basicly telling you how to do the things you want to do as for the nuke it is extremely hard to do without map rebuilding (isnt possible yet) ive tried to make a nuke but found that i was going no where with it. the banshee in multiplayer is also going to be a hard one to do.
and the infinite ammo,health,etc... can all be aquired by use of a halo trainer
also check the pinned boards on halo files sites