You need to remove the caliper bracket which is held in by 2 x big bolts on the rear,they use an 8mm allen key.Be aware that these bolts are often seized and you should make sure the allen key part is clean of any dirt before you attempt to undo them.If you round those bolts off you are in big trouble.
If you have a blowlamp it will be of help,also,use an 8mm allen key socket on a torque bar,not a standard allen key as you will get nowhere.
Do'nt forget you will have to wind the pistons back in to make space for the new pads.I found the easiest way to do this is to temporarily refit the bracket and caliper to the car BEFORE you fit a new disc.That way the caliper is held firmly whilst you wind the pistons in,they can be hard to turn.
Haynes manual is good for one thing,a rather thick mousemat

It has no other purpose as far as i know.