I was able to get the spacer ring off, I got the arched plate off and knocked the ring sideways with a chisel until a gap formed, then used a perpendicular (from above) angle to wedge things behind the spacer. It's easiest to alternate from the top left to top right corners to make it stay even.

I started with a small screwdriver, then went to a chisel, then a ball joint puller, until it was far out enough to put a small pulley puller (ie power steering pump pulley puller) to grip behind the spacer. It then slid right off with some cranking on my ratchet, similar to how the harmonic balancer gets pulled off.

These rings are tight enough that they're supposed to rotate WITH the crankshaft, so putting the new one on will be easiest when pre-heating it with a mini propane torch (the small blue ones you get at Lowe's). I had some welding gloves to handle the hot spacer, and you have about 15 seconds to get it on. It slides right on like butter, at least until it cools down.

I still used the plastic cup trick to get the seal on after the spacer - putting the spacer on after the seal seemed to not work so easily for me.

As I think of it, if the front of the engine can be clean enough (depends on how long the leak was ignored), then heating the old spacer on the crankshaft probably will work. If it's hot enough then two screwdrivers on opposite sides should get it to come off.

It looks like there used to be a gasket seal on the arch plate, so I'm going to put a bunch of RTV sealant on everything. I want to minimize further leakage.

I already put a seal on a few months ago and it just kept leaking. Probably because the spacer needed replacing. If you see any nicks, scores, lines, etc on the spacer, it REALLY ought to be changed. Just a tiny scratch can cause a nasty leak from my experience, and then that's a whole nother weekend. On top of that, I re-used the old hex bolts for the balancer/pulley, which proved to be a dumb idea. As I tried to get them off the second time, they ended up stripping. They seem to be a one-time-use type of thing. I had to drill them out with various sized cobalt bits - and then when there was a big and deep enough hole, to use a drill extractor bit (the tapered grey ones with a square end for your ratchet), to twist them off.

Glad you got it.

If the old one has a groove, just flip it around so that new material rides on the seal.

The reason that the spacer ring rotates with the crankshaft has nothing to do with how tight it fits. It rotates with the crankshaft because the balancing disc bottoms out on it and sandwiches it in position.

Not the best option. There is no guarantee that the new seal will be positioned and/or ride the spacer in exactly the same way as the old one. That job is not a good candidate for trying to save $12.

It definitely works. When you look at how it goes together, one half was in contact with the original seal, the other half was never in contact with anything. Putting it around backwards give you a non-worn surface to contact the new seal. Assuming the spacer wasn't chewed up when removed.

Sometimes the wear is not on just one half of the spacer. Sometimes the new seal rides in a different spot than the original. Seals are not precision parts; there are manufacturing differences and installation differences. Anyone who wants to risk doing the job again in short order is welcome to take the chance and save a whopping $12. For me, the risk/reward ratio just isn't stacked in the right direction.

For sure, stating "It definitely works" is misleading and factually incorrect.

It might work, definitely. And it might not.