I bought a generic replacement valve which came with a little brass tool but looking at the car I can't see where the slot in the tool will unscrew the valve. It's just a round hole with the ball of the valve showing. I was under the impression that the A/C connections were standardized when everything was switched over to R-134a. Autozone had a kit listed which includes the entire valve body but didn't have it in stock. Do I need a special tool and valve or do you have to replace the upper valve body as a unit.