HaloMods "Classic" Read-only Archive

I'm wondering which tool I need to use in order to change parts of individual models around. I know there are a lot of different programs but I'm not sure which one I need to use.

well milkshape 3d is a basic modelling tool to use.
easy to model with.
theres a tutorial of how to model with it at http://www.halo-scenes.com

and you can always use something else, like blender (google it), which i think is free. or you could go with gmax, too (if you can find an exporter).