precautions are the same as with any mod, just be careful
heres a diagram i did for putting led's in the filler slot, if you want to put lots of led's in the shell too then just go inside the ds and match up the pins on the motherboard, its not hard, just think of each pin in the filler cart as a wire runnig straight through to the pins on the motherboard on the back side of the slot -2 connector.
a clear case is always useful but it looks nice and eary on a white shell