My 78 spider with 43k has an oil leak at the head gasket. I have a mechanic that is honest a capable, and want to know that while we have the head off, do I go for a full head and valve job, mill, port and polish or should I just replace the gasket. Cost of the complete job is $1,800. Head gasket only $700. I plan on owning the car forever, so leaning to the full job. Any thoughts????