Hi,
You pretty much have to take everything off, unfortunately.
You start with the logic board, then the drives, then the analog board, then the CRT, and finally, the chassis (which should be held in place by five Torx screws).
The speaker is held on by two plastic rivets, which you need to cut away with a utility knife, then you can lift it off with it's rubber gasket.
Once you've done it once or twice, it gets pretty easy.
c