Even if you get the plug in for Photoshop, I would still recommend getting GIMP. It has a very good tool for creating Normals. It also has the ability to save .dds files without compressing them, which I believe PS does not have. Saving .dds files without a compression almost always helps the quality of the image in game. And, I know how to do pretty much anything with GIMP, so if you ever had a question about it, I could answer. Hope this advice helps.
Edit: Oh, and also, Conus00 has already done a mod in which he massively improved the crew uniforms: Conus00's Graphics Mod 1.1. You should really take a look at it. I am sure that he would let you use his mod as a base to make further improvements on.