May be we are talking about 2 different issues. The oil leakage from Valve covers and stem seals/vlave.
The oil leak from valve covers can not get into the plugs, but can drop on the exhaust pipe and give you a burnig smell. Same thing can happen if transmissinon fluid is leaking and dropping on the exhaust pipe. I guess time to get under the car and investigate more.
As for as plugs being all oiled up, it could be stem seals leaking, bad valve or worse case worn up rings. How many miles on the car? how often you have to put a quart of oil in the engine? Does it gives you a puff of smoke on start up?

I hope these questions /investigation will help you to narrow it down to actual problem.

Good Luck.

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87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)