High Side Service Port.

I have a 1996 Cadillac Seville STS. I think my high side service port valve is leaking, I think it's the valve because there's residue inside the cap and the silver liquid line below it is all gummed up. There doesn't seem to be anything coming from the port where it threads onto the line. I have a tool to take out the valve, but it only works for the low side port valve. Is there a different one for the high side? I'd rather just replace the valve if I can get it out. If I need to buy a special tool; I can just buy the whole port as they are cheap, Thanks!