I had this exact problem about a month ago!
This is just from memory, so please forgive any omissions. (BTW I just worked it out as I went along, I'm no pro - so be careful of any sharp edges etc!)
Attach the new hinge to the machine first (it's easiest).
The hinge is held by an internal bracket which you will need to get hold of before you remove the hinge as it will fall into the machine (and it's a pain to get back out)
At the back of the machine along the top are (3?) screws, remove them and you should be able to lift the top back and up off the machine to expose the innards.
Remove the washing tray and you will see 4 screws holding in the plastic holder, remove them and you should be able to move the plastic holder first up and then back.
This will allow you to slide your hand down the inside of the machine and grasp the hinge retaining bracket while you unscrew the hinge!
Screw in the new hinge and put evertyhing back together (minus the door).
Now the door and broken hinge are off, unscrew the 3 or 4 screws holding the door together. You will need to pry the pieces apart as they clip quite tightly.
You will see that there are 2 pieces of white plastic holding the hinge in at both ends, pry them out and make sure that there are no bits of old hinge in there!
Place both of these pieces onto the new hinge now in situ on the frame of the washing machine. Clip the door back onto these pieces (you might need a third hand for this bit :) ). Once the door is clipped onto them, press the front of the door back on firmly (you should hear a loud clip) and screw it back together.
Done.
You might want to lubricate the hinge a bit with some water resistant grease.
Adrian, February 2008