Ok, I'm a bit guilty here, I've been poking around and moding things with GC for a couple of weeks now and in some cases (most) I didn't create an 'original' file to revert back to after seeing what different things did. Is there an easy way to recover GC back to default files without doing a reinstall?
Not that I'm aware of. I suggested placing a standard data file backup in the library for the same reason you're asking, but it went over like a lead balloon. I reinstalled and now I make sure to keep three directories going: official GalCiv (DataGC), for when I feel ambitious enough to contribute to the imperial warchest on the Metaverse; test (DataTest), containing all the official data files, but used for testing individual modifications before approving and removing them; and my own private Modaverse (DataCB) that contains all the play-tested Mods I like to play with.
Version 1.04 should be out any day now, though, so you shouldn't have to wait long to reinstall.