Just went through this when rebuilding my flippers. I used a 5/32" punch, which was the perfect size, and I used a bench vise, with the jaws slightly opened, so the roll pin had the gap to clear. I rested the crank assembly on top of the open vise, and tapped the pin out just enough that I could wiggle the old plunger assembly out. It didn't take too much effort, but it took some fiddling because I didn't want to knock the pin all the way out since I was going to reuse it.