I have reproduced the details of my article: http://www.fixya.com/support/t1543617-door_seal
here. I hope this will give you the information you need.
Rule 1: BEFORE YOU START Turn off the mains, unplug at the wall, turn off the water supply.
The gasket is held in place on the drum by a large sprung wire ring with a screw tighten/release. To access this (Depending on the model), you will either have to go in from the top or the bottom of the machine. Usually the top.
Pull the machine out, go to the back and unscrew, usually 2 screws that hold the "Work top surface" top on the machine at the back. There are usually clips at the front of the top, so by lifting the rear clear and either pulling the top back, or giving it a tap forward, depending on the design, the top should now lift off.
You should now be able to look down at the drum and you should clearly see the rubber gasket fitted over the edge of the drum with the clip in place. Locate the screw in tensioner and undo it until it is possible to slip it forward and clear of the drum. You should now be able to simply pull the gasket away from the drum. Most machines rely on the door being closed to hold the gasket in place where it meets the chassis, it should just pull off if the door is open, but while you are lookiing inside, just check anyway. The assembly is simply a reverse of what is described above.
Stuff to consider: You may not be able to see the screw clip from the top, if so, tip the machine back and look from underneath. If you have to do this: Never tip the machine all the way onto its back, you may cause a water leak inside the machine. ALWAYS tip BACKWARDS, so the control panel for the machine is pointing up to avoid water getting to the control panel. I would recommend putting a chair behind the machine as you tip it, so the top back of the machine comes to rest on the seat and the machine is at about 45 degrees. this will give you access to underneath without a leak and make is a lot easier to tip it back on to its feet again afterwards.