Super easy man. It's the most basic thing about "modding". Pretty much the first thing people learn. Follow that vid that Shadow posted or search the forums, there are some tuts up if reading helps you more then a visual.
Oh okay that would help, too bad I have a mac tho... FFFFFFUUUUUUUUUUUU! After trying to do it on the PC, I gave up. Its too damn slow. I give up.