You usually end up with water in your oil if you've got head problems, and it goes brown like coffee with milk. The water in the radiator gets an oily sheen on it, but doesn't really go sludgey or milky like the oil, unless its a big failure of the gasket. Just sound like a dirty cooling system. Has it ever been properly flushed? But it you coolant is being forced out the radiator, it sounds like you might have gasket problems. I had a car which kept forcing the coolant out or the radiator into the collecter tank, oil and water were fine, no contamination. But the head gasket had failed between the cylinder and the water jacket, letting compression into the cooling system.