Ran a compression test on my car because it had been running hot.  Was
told that it could be a head issue.

Cylinders 1, 2 and 4 had the same result:  185 psi.

Cylinder 3, however, was way out of whack.  162 psi.  Squirted three
shots of motor oil into the cylinder, ran the test again, and that
brought it in line with the others -- 185 psi.

Haynes is telling me that this indicates worn rings.  Worn rings
doesn't sound good.

My question is is this 12 percent difference portend a major engine
overhaul in my near future or is it more like a noisy muffler in that
it isn't right, but it isn't the end of the world either?  Right now
the car isn't registered, just came out of a year long storage.

Don't know if this is related, but a clicking sound is coming from the
valve cover.  Click, click, click, click, click -- kind of like when
you were a kid and you clothespinned playing cards to your spokes.
I'm guessing that that is valves or lifters, maybe due to the car
sitting.  Changed the oil and added some Mystery Oil, but no change.