My White Knight Sensordry is making a knocking sound?

My White Knight Sensordry is making a knocking sound and I have taken off the front panel and have noticed that there is a plastic fan underneath at the front where the filter is located. The fan is loose and the fins are worn at the end. I think that the fan has moved forward and the fins have been wearing on another peice of plastic as the drum has been driving. Does this fan have to be replaced and how should it be secured correctly, can it be done from the front of the machine?
Cheers