Changing the part is very easy,

1. Unplug your vacuum cleaner from the mains supply.
2. Take the top off the vacuum cleaner and remove any bags and filters,
3. Turn the drum upside down
4. Pull the broken wheel sharply up away from the base of the vacuum, (if stuck you may need pliers to remove the pin as it can be stiff)
5. Press the new wheel into place.