Engine overheating failure

I bought this car with the understanding that it had an overheating issue. I packed several gallons of water and drove carefully, watching the thermostat. I planned to stop and let the engine cool/add water as soon as it got to the hallway mark of temperature gauge, to be safe. I noticed that the needle was almost there and decided it was time to pull over, but I didn't have time before the engine shut off. Upon closer look I discovered that there was no coolant in the vehicle at all, and very low on oil as well. A friend, trying to help, immediately poured water into the radiator, and I could hear the water start boiling immediately on contact!
What are the chances that the engine is not ruined? It turns over still. I checked compression and I'm certain the head gasket is gone, but don't want to waste the money I spent on the replacement by using it on a bad engine. Are there any tests I can perform to check it? Would replacing the upper half of the engine be more likely to be adequate in this case?