z64, you might want to PM FSF to make sure he sees this and knows you're interested.
Of course, you'll need to learn about FRED, both the tool and its codebase. The best if not only way to do this is by FREDding some missions. If you're just starting out, take a look at the
FREDdocs (and also karajorma's new FREDdocs that were bundled with Diaspora, not sure if there's a copy on the Web), then do the extended walkthrough and ideally also create a mission or two of your own. I've heard that the FRED code only makes sense after you've made at least some simple missions.
Hope that helps.
EDIT:
Here's a link to karajorma's FREDdocs, although I don't know if that's the most recent version. It's for Diaspora, but it covers FRED2 Open-only features that won't appear in the retail FREDdocs.