how to remove this faucet cartridge?

[throne7]

Hi, I am trying to help my parents fix a leaking faucet. Its on the hot water side and leaks continuously. I removed the faucet cap and found the faucet cartridge has a plastic piece in the middle. The base is large hex nut . I wonder how to replace this cartridge. Do I use a vise grip wrench and just pull the plastic piece? Or do I unscrew the hex nut? Why do they have to make it so complicated?

The plastic piece is not even, on side is flat and the other side is raised a bit higher at the base. The photos is below. please can someone please help.

//www.diynot.com/network/throne7/albums/4375

 

[bellairaphon]

first turn the water off to the tap. if you have an isolation valve. are you on a hotwate cylinder? there will be an isolation there. then take the hex nut off which will release the body to change the washer.

Nath