This is the main tool for mods, everyone here i asume has it, its called the construction set. Its free, and its user friendly, although you might be confused about a few things here and there, but you'll figure it out im sure.
Construction SetYou can also go here for when you have problems with it.
WikiNobody should be without the construction set, but there is a lot more to moding. A great list of things that can be done outside of the construction set to build mods.
After you play around with it, your welcome to email or msn me at
DiroxOblivion@Hotmail.com
if you have questions or want to join my mod team ^^
Dont mention it, peace.
~Dirox