Can you post pictures (or did I miss them) of the combustion chamber side of the cylinder head?
Good engine machine shops are getting hard to find so the best recommendation is to talk to others in your area that may have had work done to get a better idea of who to trust. I don't know if you have race car engine builders in your area but they have a lot more experience than general vehicle user types.
Replacing the head gasket isn't likely to provide any benefit to your original oil smoke problem, however if it was coolant smoke (white) then replacing the gasket could help. It's not ideal by any stretch but the cost of cleaning things up and replacing the head gasket is mostly your time. You indicated #5 and #6 may not have been firing but the head gasket failure is not adjacent to those cylinders so understanding why they would not have been firing is an important piece of information.
