Well, I find the best way to learn FS modding is just by trial and error. If you don't give up, you'd be surprised what you can achieve. I can't run FRED, but that hasn't stopped me from trying to FRED (TextEdit FTW! )
I agree with blowfish. FREDding may not sound easy, and it isn't, but when you give it a try, you may find that you like doing it. I tried it, and I was interested enough to FRED two mostly-complete missions. I pale in comparison to modders like Woomeister, Goober5000 and GalacticEmperor; they've done A LOT for the SCP project, doing things like making mods such as Inferno Release 1, the FreeSpace Port, and re-touching the PVI Karnak.