I usually punch it out with a long screw driver from the back. Get a good long flat-head, wedge it in where the ring meets the pump lip and tap it out with a hammer. If it's really in there, I have had good luck with a dremel. I used the bit that looks like a drill bit but is meant to cut with the side. As for inserting the new ring, throw it in the freezer and it should just drop right in. OEM rings work best, and are guaranteed to be a perfect fit. Aftermarket is a crapshoot, some good, some bad. I've had one that was egged (different clearance in different areas) and cavitated the whole time. Changed EVERYTHING before finally getting an OEM ring. Strangely, that one only lasted about 1 season, so my next one will be stainless. Wish I did that the first time. The argument for plastic is to sacrifice the ring to save the prop, but if the ring is damaged, the prop likely needs to be sent off too. The cost to restore a prop is the same as an OE ring, but props last a lot longer than rings anyway. Yamaha and Kawasaki use SS from the factory.