Modding the Stars and Planets in 3-D view

Well, I've never played with x-files before. What software will I need to reduce the size of the Star and planet wire frames? I also want to change the skins, I think that will be the easy part. I want to re-scale (reduce)the 3-D view for a little more realism. My over all mod would be called the realism mod (ha). Hopefully I could be finished with this about the same time as the map editor come out...