Anything 2005 or newer (since you didn't bother to tell us what car you drive....) will disable the cruise control with any check engine code. This is not a cruise control fault.
yup, what Numbchux said.. The newer cars disable CC to get your attention. And it works, too
Read the codes for the CEL, correct the issue what ever it is, and the CC should return to normal operation.
Any brake related error codes will disable the cruise control. CEL (check engine light) is only on to tell you error codes are stored and maybe still present.
odds are that the oiliness is from the cam cover seals being shot, not the headgaskets.
make sure you reseal the oil separator plate on the back of the engine.. if it has a plastic cover, get the metal replacement & the screws to go with it (the screws for the plastic cover are too long to use with the metal one).
It should be. Hangers could be different but wagon to wagon works as does sedan to sedan. Sedan to wagon and vice versa needs a mod to the exhaust tip length from the rear muffler.
Cheers
Bennie