Alright, first things first.
You have to make sure that you put in the right folder, inside the FALLOUT 3/Data folder.
If you've already done that, and it still doesn't show up then you have to download something called "Fallout Mod Manager", or "FOMM" for short. Once you download that, you should see your mod listed there. If you STILL don't see it, then I have no clue what to do.
Second, for uninstalling the G.E.C.K, you just go to your Program Files, or your Program Files86x, if you have the 64bit vista. Look for Bethesda Softworks, then go to Fallout 3, then you should see "Uninstall G.E.C.K." I hope that should fix all of your problems!
Good luck, and enjoy FALLOUT 3. Its a great game really, and with mods it just becomes much greater.