you need a tri wing to open the GC controller, and a small regular scredriver to get the cover off the triggers
1. open the controller
2. remove front and board carefully(just dont break it lol)
3. remove screws from covers and remove the cover
4. push the trigger all the way down and remove it from the controller(ALT: you can take the bottom out and remove the spring from there and just place the bottom back in the brackets it rests on)
5. after springs are removed put the cover back on.
6. when putting the front and board back on, carefully line up the pegs on the back of the board with the holes on the trigger(this part will be sticking out after the cover is back on the triggers.) if you dont do this right the triggers wont work.
7. screw back together and enjoy
once you get it open its pretty self explanitory, or easily figured out
its just gettin a tri wing is sometimes inconvient
http://www.smashboards.com/showthread.php?t=69935
theres pics on the first page of that thread explaining the peg thing better