You will be able to change the skins but not the models right now -kind of.
Check out the main page left hand side, under guides. Here you will find some very good guides on how to skin and mod MOH.
You may want to check out the forums over at
http://www.themodtheater.com. Look for Scorpio's threads, he as been able to change models but it's a very intense process and not for the beginner.
Good Luck hope to see some skins soon.