Yea, I just spent 4 hours out there cleaning up the parts. So now I'm ready to make my assessment.
If you look at the attached photo below, you can see that there are actually THREE plugs on the back side of the block.
The top one, which had no problems, is at the end of the crankshaft. Backed in oil, there's little chance that it needs to be replaced.
The middle one is actually an opening to the water jacket. Hence this is the one that will leak 99% of the time before the other two. It is called a "freeze plug" or a "cast plug" or an "expansion plug". The original purpose was to allow the casting sand to be removed from the inside of the block.
The bottom plug is against the camshaft and as Rusty said, does not have water behind it, so it should "never" be a problem.
Now having set the stage it appears that the middle (water-backed) plug began to leak and drained down both sides of the bell housing, including into the lower (camshaft) plug. As far as I can tell there is no problem with the lower plug.
As far as sealant --- my thought is that there is a minute possibility that the hot water running out of the middle plug may have (very slightly) eroded the opening in the block. So some sealant there would be cheap insurance. Also, if you think about it, I'm sure that in the factory, these plugs were PRESSED into the openings in a smooth and STRAIGHT manner. In my world, I'm going to use a hammer and a socket to insert it. So 1) I need to cover my a** with some sealant just incase the plug is just every-so-slightly at an angle. But equally important, I think that when you try to press something like this with close tolerances, it doesn't hurt to have a small amount of lubricant to assist it. And that's the second thing that the sealant does for me.
Be happy to hear any comments (and corrections) on my analysis above. I've not a mechanic, never have been. But I've been a backyard-mechanic all my life and I find that common sense and simple analysis can get you a long ways in this hobby.
Now.... where the heck are my keys???