This morning the car sputtered a little when it started and is having trouble idling (like it wants to die periodically). Shortly thereafter, the engine light came on. I took it to AZ to run the codes and it shows a misfire on cylinder 4.

I figure this can be fixed with a tune-up and spark plug change or I'm losing a head gasket. Is there any in-between ground here that I'm missing?

 

there is a good chance you have a coil that has come to the end of it's useful life, it just happens with the lucas coils.
I'd change out your plugs, and swap the number four coil and see if the misfire code follows it.

 

Exactly the problem. Thanks.

Starting to feel some jerking when it shifts from 2nd to 3rd now. Hope that tranny's not going.

 

no way that a head gasket could've been causing that; my head was warped and leaking coolant into the oil channels, and she still ran like a champion and I never knew until I pulled the dipstick out one day and saw the dreaded cappuccino on the end of it.

as far as the transmission, a filter and fluid change wouldn't be a bad idea.
should improve smoothness of shifting.

4 quarts of dexron III fluid and the trans filter which I always end up buying at advance auto.
$30.64 is usually what I end up paying for the whole job