Milky oil can also be a sign of a bad PCV system. The coolant loss could be unrelated to the milky oil. A compression test should be the first step in determining if you have a bad head gasket. You could also test the coolant in the radiator for the presence of compression gasses with Block Tester. You can rent the equipment for both tests at most parts stores. Replacing the gasket would likely be the cheapest repair route, but at 215K miles you most likely need other things, like a timing chain, or valve job, it can quickly escalate to a full blown rebuild. Replacing the motor is cheaper and quicker than a rebuild. A remanufactured (or "reman") engine is one already rebuilt to manufacturer's specs, you would need your motor to turn in as a core.