How do I change the CMOS battery on my Fujitsu...

Question

Hi there

The CMOS battery dies every year or so on my Amilo D 7820 and I figured I could probably change it myself instead of paying someone else to do it for me as the batteries are quite cheap. However I'm not sure which bit of the back I need to take off and I don't want to break it.

Does anyone know which section of the back panel I need to take off to get to the battery and if it's easily accessible? Any thoughts would be very welcome