Ive just done this repair. I found i had to remove pretty much all the screws (including the sneaky one behind the timer knob !) You'll end up with a very floppy tumbler, handle with care.
open the door and seperate the drum on the front bearing, slip the belt over the drum and tape it in place temporarily at the correct place on the drum which will be worn shiny by the old belt .
carefully refit the drum into the front bearing and close the door again.
the belt is a *VERY* tight fit and to get it over the motor pulley with the guide wheels for the belt removed i undid the three screws which hold the motor to the tumbler floor, slipped the belt over the motor pulley then did the screws back up whilst pushing the motor from the other side.
Make sure you remove your temporary tape and
watch out , all the metal components on mine were very sharp.
refit the guide wheels /tensioner- check theres some white grease where they pivot on the floor pan
Take the time to remove all the dust from inside the insides of the machine, heat and dust together not a great idea.
Pretty much all the screws on mine were the same size
luckily, but as you screw all the panels back into place it will become nice and rigid again
Job done . my belt was about £10 from an internet auction site
Robert
February 2011