Hi I did this myself only a few weeks ago.
The seal is held on both inside and outside the machine so you need toopne the door and remove the plastic clip thing from the top (you'll see it) and the wire will come off easily then take the top off the machine and unscrew the clip (phillips screwdriver) from the inside. The seal will pull out easily then.
You basically perform the same operation backwards to fit the new one - but it's quite fiddly and I left half my hand inside my machine doing it so more than one pair of hands might be useful (someone to hold the drum away so you can fit your arm in to refit the interior seal.)
Anyway - having never repaired my washing machine before - I managed it (via a lot of swearing and a couple of plasters) and it's been fine ever since so good luck!
Kelly
May 2004