You can get a replacement kit for about £60 and I did have one that lasted about three months - sent back as faulty.
When you fit don't forget to take the dust caps off the pump

and be careful how you take the flower pot out of the tank so as not to bend tha actuator arm.
Pour a kettle of boilering water over the ring and connectors and then have a cup of tea while it cools and thenm mop up the water - help soften up brittle the plastic.
You don't need the special tool - a lot of people use eth water pump pliers but I used large screwdriver and mallet and just knocked it round until it came loose. Pull the fuel connectors VERTICALLY up and not at an angle or you will break them and I found a spray with WD40 helped together with a slight twisting motion back and forth. Pull the locking tabes away slightly - it will become apparent when you look.
Once refitted listen for the pump to prime.
Have you checked fuse adn 12v feed to the pump just to eliminate?
Mike