I've been told that those whom will be modding should take advantage of the Unreal Tools prior to the release of the Kaos tools. Here are the tutorials to make you a master of the alreayd available tools for UT3.

http://www.utforge.com/index.php?PHPSESSID=7ef0dca3fb1effd640386275a5c69cf9&page=31

This is just a start and I've been told the tools for Frontlines are going to be pretty incredible but this will get you to the master level for UT3 part..