Leaking Delta bathrub spout

Hello and thanks in advance for any assistance offered.

I have a leaking bathtub spout. It's a whirlpool type tub. It has a spout and two separate knobs for hot and cold. The spout and knobs are on top of the tub...not in the walls of the tub.

It is leaking hot water.

I removed the hot water knob....and there looks to be a hard pipe stem with a plastic part inset into it.

Any idea how to remove the plastic part?

Thanks in advance,
Chris

Here is a good video showing how to repair it.

http://www.deltafaucet.com/videogallery/index.html?video=ReplacingSeatsAndSprings

Your faucet has the seat and spring like in the video, but only one below each handle.
The brass nut holds the stem in.
You can also find replacement stems.
The video shows a single handle repair, but it should be enough to show the spring and seal that needs replacing.

Thank you very much!

Chris