Okay, I was able to see the split retainer. I compressed the spring and hit to top of the tool to loosen the retainer but it won't budge. As I move up and down with the tool the valve goes down with it if I don't prop the bottom of the valve with a wooden block. I am right now testing this procedure on an extra head I have, so I have access to the valves on the other side.
I will use compressed air on the real job tomorrow; today is practice so I don't mess things up since this is the first time I am doing this.
I will try again after lunch...