Do you mean the valve stem or the valve body? The valve stem should push out the body with very little force, just prod it with the rubber end of a pencil or something.
For the valve body, NEVE push it out of the front, you will more than likely find you have shredded its o-rings once it is out. Push it out of the back of the body, the same way the hammer assembly came out.
To remove the valve body you have to take out the valve retainer screw, which is under the body. You have to reove the grip frame, and then you will see a large silver screw behind the front grip mount. Take that out, and the valve body should come out quite easily then.