ADD:
The rubber sleeve in the kit is useless, chuck it.
The foam sleeve needs to go on before fitting into the swirl pot and put a bit of WD40 on the pump to make it easier to slide the sleeve up and down.
Make sure EVERYTHING IS PLUGGED BACK TOGETHER BEFORE FITTING!!!! Connector plug on the cover plate, connector on the sender unit, connector on the pump and the connector on top of the tank when you go to fit it onto the car!