I need to replace a freeze plug?

Tap tap tap.

In the days of yesteryear, freeze plugs could be knocked out with a large screwdriver punched into them, and pried loose. Then an aftermarket plug would be installed, which would tighten up with an adjustable clamp that clamped to the inside of the engine.

The cap was just a metal piece installed into the engine. Originally and perhaps still, it was not designed to be a freeze plug, it was there for the purpose of making a mold of the engine. there had to be holes in the engine mold, so these were put there.

And then, after the engine was made, the holes were...plugged up. And it seems, that when an engine froze, these would pop out, being the weakest part of the engine. So, freeze plugs they became.

As for the ring, I am not familiar with that. The ones I did, back years ago, were just a metal cap, that popped out. Not screw ins or anything. Perhaps they are different now.

There used to be replacement caps, made of metal and rubber, with a clamp on the motor side that would expand when the nut was turned, and tighten up against the inside of the engine. There was various sizes, to accommodate the different freeze plug sizes.

Also, motor heaters could be put into these holes, allowing a convenient way to pre heat the engine during cold winter days. They also came in various sizes, for the different cars.

I don't know about the engines of today.

It's done the same way, but if you use a punch (sharp end) at enough of an angle it may work its way under the edge of the ring and collapse it. That can be good news or bad news, though - the ring may fall inside if it collapses too much.

Special tool time. Sometime if you hit one side with a screw driver and hammer, it'll turn sideways and you can pry it out.