I did the same job for my mother yesterday. Unfortunately, her partner had decided to try and do the job from the back(impossible) and left top and sides off in the damp. Now I have to take it apart again and see why the motor doesn't go Urghh.. As with the right Royal pain of getting the belt on the drive spindle (my words were much different to that !), I found easiest way was to use a bit of wood (roofing batten dimensions ) about foot long, slide under belt flat, twist on to edge and then lever belt on. It went on quite easy once i got the technique.
Kevver
October 2011