My dad dropped off the cylinder heads today. Fortunately, resurfacing them did remove most of the damage. I removed the valves and cleaned up some more to make sure there were no protruding bits of metal.
I also inspected the valve seats carefully to make sure there was no damage. Fortunately, they were spotless.
I cleaned up the valves and inspected them as well. The mating surfaces looked perfect, so I reinstalled the valves in the head.
Finally, I cleaned all the RTV off the heads and then trimmed the new head gaskets to match the old ones.