Turn upside down & support. remove the 3 big silver screws & take off the big 'L' shaped piece gently. Note it's position ready to refit.
Remove the brush noting again how they fit.
remove the old belt & refit new one round motor spindle, then fit over brush. Stretch the brush so it relocates. Carefully relocate the bottom and the 3 screws. Check everything is located properly.
Steve, April 2009