My suggestion to anyone wanting to start modding games, would be to start with something small, making maps is a nice start, you'll begin to gather knowledge on how certain aspects of the game work, and when you can master mapping, then try starting with ACS scripts, which can be very powerful if used correctly, then get to something else, like changing behavior of the enemies, etc.
And last, but not least, if you are stuck with something, always ask on the forums around the community, there are a lot of people who know of these things and are willing to help you out to complete your task <!-- s;) --><img src="{SMILIES_PATH}/icon_wink.gif" alt=";)" title="Wink" /><!-- s;) -->, good luck to anyone starting on this! <!-- s8) --><img src="{SMILIES_PATH}/icon_cool.gif" alt="8)" title="Cool" /><!-- s8) -->