[dwcsr]

The plug has oil on it above the sealing ring, that may be your engine leak from a valve cover, to much pressure in the engine, some other reason? should be easy to find just as the trans should be easy to find. once you know what's leaking you can determine why or if it related.

I would look at fuel first, fuel issues tend to creep up on you like you describe. Electronics usually is some un explained issues then it dies.

Checking grounds as mentioned above is also a good idea whenever you have unexplained electrical issues. Bad grounds can create odd issues and electricity will find a ground if one is available and sometimes its through another device that's not equipt to handle grounding of another circuit. Ohm the engine to distributor to see if its grounded. a distributor ground sometimes ends up being through the oil pump. not good, run a ground strap to it if needed.

A vacuum gage will tell you a lot about what's happening as far a the engine and valve train. A Stoich meter (Air/Fuel) will tell you about the fuel leaving the engine, if its burning correctly, if you lean or rich. Using both also helps you dial in the jetting and confirms you have the valves adjusted properly. You'll be surprised at how much easier it is to tune with those two meters and how much better it runs afterward.