Editing in-game text

I'm interested in tinkering with the text that comes up for various events in the game -- from announcements of how kids are doing in school, to verdicts on holidays, that kind of thing. I don't have a serious purpose in mind at the moment, I just want to know what's possible so I can personalize it to some degree. I don't imagine there's one central package I can open up? (Civ3 made this absurdly easy....there was literally a "Script.txt" and "Diplomacy.txt" file editable in notepad!)