Exporting and rigging skeletons for deformable meshes.
Somewhat brief overview of exporting skeletal animation units with RenX. The only units which use these are infantry. They consist of 3 files; mesh, skeleton and animation. These 3 files are linked by a spacewarp (Renegade skin) which looks way more intimidating than it is.
I recommend using the Coolfile importer as that's what I use in this video.
If you simply want to clone a unit and change the texture, you can do this through hex editing the W3D. It's a lot quicker and less prone to error. That's covered at the end.