My advise to you is, get to know the basics of modding before you get into the tough things like sides. Read up on the Everything You Need thread:
http://www.gametoast.com/forums/viewtop ... 27&t=13806
Make a map that plays good and is not very complicated, before you start doing all the complicated stuff. I wish I had someone tell me that when I first started out. You can't just make a super-duper map right away, it takes practice and a lot of reading.
Now to answer your questions, where did you pull your .msh files from? You should be getting them from: C:\BF2_ModTools\assets\sides\imp\msh. An example of an Imperial skin is: "imp_inf_trooper.tga".
You do have to copy your units weapons .odf's. Everything that has to do with the characters you are putting in game, has to be in your sides folder. Including your .odf's, .msh's, .tga's and .req's.
To answer your last question, (someone correct me if I'm wrong) you should be taking the "imp_inf_rifleman.odf".
EDIT: Oh whoops, you want Snowtrooper. Never mind my last bit, take "imp_inf_snowtrooper.odf".
EDIT2: Whoops again, "imp_inf_rifleman_snow.odf".
