Moen 82602 two handle shower. Need advice on shower faucet/valve

[NotQuiteAPlumber]

Can anyone identify this shower valve and know if the cartridge is replaceable? I think it's an American standard but from what I can see that cartridge isnt budging!

It's part of a 2 handle shower faucet. It's dripping so I thought it would be an easy repair.

Any input is appreciated.

 

[Marlinman]

The valve is Moen. They had many different trims but this is the internals.

http://www.cfgonline.com/shared/docs/exploded-parts-views/82602pt.pdf