Drive belt replacement?

I have a philips d163 tumble dryer needing a new drive belt. I need to remove the back, in order to do this I needto remove the fan from the motor spindle.There is aflat on the spindle which will take a 12mm spanner and athreaded boss holding the fan on.{ I think its threaded] is this a right or left hand thread ? Once the fan and the back are off I am sure I can fit the belt.