Oil Leak - Black Plug on left side of engine

[radare]

This has been the year for oil leaks. In the past 20 years, my XJ hasn't leaked a drop. This year: Clutch cover started dripping after a ride, valve cover started weeping on the right-front side, and now I have a drip on the left side when on the stand.

I initially thought it was coming from the timing cover but after a bit of wiping and watching with a flashlight, it appears to be leaking from the leading edge of this black plug. Here's the plug (colored in yellow):



I swear I've seen others have trouble with this plug. Looking at the fiche, it appears to have an o-ring behind it. Is it a simple matter of draining the oil, removing the plug and resealing with a new o-ring?