Go to the manufacturer's site and they'll usually have pages which show you how to remove it.
It'll most likely be a cover held in by a screw.
As for backing it up, there's the easy way:
get an external hard disk, plug it into the usb/firewire and copy everything accross.
Hard way: Take drive out, get a 2.5" ide to 3.5" ide adapter to plug it into your PC and use a ghost image program to back it up straight onto the new drive, using an adapter on the new drive as well.
Confused yet?
