I have only used mods on Morrowind. Are the mods here for Civ4 the same idea you can also remove them if you dont like what they do to the game? I have seen some mods I would like to try, but I dont want to make changes to the game that cant be undone.
Sorry for being such a newbie :p

Do not put the mods in the assets directory in your civ 4 directory and you'll be fine. Customassets, mods and custommods all work. Except there used to be a bug with custommods, don't know if they've fixed it yet.