How do you replace coolant sensor 1991 190E Mercedes Benz?

It is located on the top of the engine to the right front of the valve cover just behind the spark plug wres. it is a big brass thing screwed into the aluminum.It has three wires that plug into the top. It just unscrews and for 41 dollars at napa it is done. Now my plug on top is broke so tell me what wires go where (they are color coded ) so I can fix mine