Read & Look around the multiple threads right here, randomize often, rinse & repeat. Bookmark what you feel needs further attention.
Dunno what your free time is or how serious you are about modding attempts, but i'd say that within a month or so of regular & continual 'analysis' of the essentials, someone can get the hang of it pretty fast.
Two must have items; Carielf's Modding Guide (it still maybe a bit old but it IS important in every ways) and Netriak's Galactopedia.
You might also want to download a few other things from the Library which are living examples of MODs (more recent, the better) that *do* work.
