Stop in for a cup of coffee

Obviously you know if that is okay by now since you have talked to them. I'd like to see what other issues caused your problem......
The exhaust seats had cracks in them. But that’s the only damage found so far.

The o rings around the injectors were dry rotted so that may have been allow the oil into the cylinders.

Machine shop thinks the head gasket just deteriorated enough to push coolant in to the cylinders