It's not quite as simple as that, I'm afraid
![Smily [:)]](/emoticons/emotion-1.gif)
It requires you to know enough about Blender to be familiar with how it works, the concept of groups and mesh names, rotation, etc. You also need to have access to MEd and/or the Mesh Manipulation utility to get any completed mods into the right formats for the game to find and use them; not something for someone who has had absolutely no modding experience previously to embark on lightly (not sure if you have previously done any modding, but am guessing not).
Modding questions are best asked at Director's Cut Modding Foundry (google the name, you'll find it!), where the mod team tend to hang out. A word of advice, though; don't bug the team on their forums for questions about Blender operations, as general queries about how Blender works are frowned upon.
There are a bunch of tutorials there that explain some of the more complicated procedures, but you really need to have a basic understanding of how Blender works and operates first before you try to modify any current meshes or models. You'll also need the import/export scripts to get models in and out to actually do anything with them.
Machinima maker? Using The Movies? iClone? Moviestorm? Any other engine? Then check out TMUnderground at (http://www.tmunderground.com/)