Basically, this is going to be a Sci-Fi mod since there doesn't seem to be many. For a start, it's just going to be cosmetic, except for a tech tree change. I don't have any screenshots so far, sadly, but I will be doing as I go along.
Currently though, I can't get the text localising to work and I'm certain that none of the text strings are duplicates since there aren't any civilisations known as TRUEWAY or leaders known as THEOPHILUS, so I'm kinda stuck. 
Edit - 20/05/2012: Thanks to WhoWard for the help. I've now changed the text for a Unit and Technology, put in a new Civ and Leader and disabled all of the old civs. It's not enough to show, but once I make sure that I can replace an improvement, tile and social policy, I can start to work on methodically working through the new civs.

Edit - 20/05/2012: Thanks to WhoWard for the help. I've now changed the text for a Unit and Technology, put in a new Civ and Leader and disabled all of the old civs. It's not enough to show, but once I make sure that I can replace an improvement, tile and social policy, I can start to work on methodically working through the new civs.