Whirlpool dryer motor pulley replacement.

Hi, the plastic pulley "guard" that sits on the shaft of the dryer motor melted and I’m looking for instruction on how to replace it.

I’ve purchased a new pulley and plastic guard:
http://www.appliancepartspros.com/Appliance-Parts/whirlpool-pulley-mtr-item-number-ap4510074.aspx

Just trying to figure out how to remove the pulley, replace the melted plastic piece, and put the new pulley on.