Fyron has the SE4 Modding 101 page here:
http://galileo.spaceports.com/~kazha...gTutorial.html
I reccommend you start out by tweaking a copy of the standard files. Find something small to change or add, see how it works, and then keep going back for more.
Above all, if you are stuck on how to get something done, ask! Many of us have been around for ages, so we will be able to tell you if something has been tried before, and can give you some ideas on how to do it.