There are five snap in lugs which extend from the main body into the rear cover (not the battery) and it is just a matter of being forceful and pulling the back cover off, which includes the one/off switch cover and IR cover, after first removing the four screws under the battery.
The fifth screws holds the aerial in place and secures the phones chassis to the front metal cover.
If the rear cover is reluctant to lift off, extert some finger pressure on the metal edge of the front where it meets the on/off switch and red IR cover, and press inwards.
the worst you could do is to break off some of the securing lugs, which will not affect the phone.
All the best and remember you need to be assertive,it's only a phone. Don't let it beat you
Mike Dixon, March 2005
