A) looks like a Schrader to me, probably listed as "shop parts".
B) $100 A/C service may be cheaper than blindly changing parts.... And causing your own blindness. High pressure chemicals can be dangerous, this from the fearless shade tree mechanic.

 

Maybe that part in the pic doesn't exist....

 

Aha! A revised drawing, good 'ol GM.

 

The repair procedure does not include and evacuate and recharge, so you shouldn't lose freon, but you alread stated you let some out, so you'll have to perform one anyway.