Head gasket on a four-cylinder is a minor inconvenience compared to a V-six. It can be the difference between salvaging the vehicle and deep-sixing it.
Your mechanic has to have a real fondness for you for that not to make a difference, but it could happen.
He does that kind of thing for fun. This man bought a truck that didn’t run from a junkyard, got it running in the parking lot, and drove it back a week later for more replacement parts.