1. GMax (3D-modelling program)
2. RenX (also called Renegade Game Pack, this allows GMax to make W3D models that Renegade and Generals use)
3. W3D Importer (a small script for GMax that allows you to open W3D models and edit them)
Gmax is at www.discreet.com and I think they have a link to RenX aswell. The W3D importer is just a tiny little file so it would be easy to get just by doing a search for it.