Overheating aluminum heads is nearly always bad. However, the fack that it was steaming suggests all hope is not lost. If you sprung a leak that dumped coolant on the outside of the engine, it may still have provided enough cooling to have saved the engine. I'd guess you dumped coolant on the knock sensors/wiring and caused your codes. Fix your leak(s) and do a check for exhaust gas in the coolant. No gases or oil in the coolant and no coolant in the oil plus no overheating and I would be confident to fix whatever else is causing the codes, if they hang around.