Once you have the screws undone and the "hat" off, you need to be aware that it is still "clipped" together - and VERY gentles use of a SMALL flat blade screwdriver can help to lever the tabs out. Also be aware that if you do not take care to disengage the volume control from the case (by careful teasing and sliding), then this too will hold the halves together.
Lastly, once you have it off by hook or by crook, it is worth dropping a dob of hot melkt glue (or araldite) over the sides of the power connector as these DO come away from the board if handled a bit roughly.
Mark, September 2009