There isn't any really easy way to teach how to make a mod... at all... :E
If you have knowledge in C Programming, a working compiler, and JKA, you're set =p
Anyway, after you compile the dll's, move them into their own folder in the GameData folder and put them into a PK3 inside that folder.
IE: C:\Program Files\LucasArts\Star Wars Jedi Academy\GameData\MyMod\
then you can start up JKA, go to setup, mods, and load MyMod.
As far as JKA sources go to learn from, you already have what you need to learn from. JAPlus isn't available to people for modding, nor are many other mods. I'd recommend just starting with your own using the JA SDK Source, or possibly from the OJP (which requires CVS to get).
Being a new programmer to the JKA source, just tinker and compile and pack it... if it works, great! if not? Drawingboard time! Same thing goes with modifying anything, really... :E
It also depends on the type of mod you want. Server side only? Stick to the mpgame section... client and server? cgame, mpgame, and UI =)