price pfister shower knob problems

i'm gonna attempt to attach pics below, but i'm gonna try to explain my problem first.

it is a single, push/pull knob...and when i pull it all the way out to turn on the water, it sprays water everywhere. the water seems to be coming out from under the actual knob. i can see water gushing inside the clear knob as it is squirting everywhere.

anyone have any ideas?

thanks alot

here's a pic of the shower

It just needs a new cartridge.

thanks for the quick reply terry.

is this something i can do myself...having almost zero plumbing experience?

where can i find a cartridge?

Cost?

is there a place i can go to learn how to replace the cartridge?

thanks again

cartridge

Home Depot has the cartridge, and the instructions are on the back of the package.