Originally Posted by mista_sse
how many pounds do I need anyway?
You need ounces, Mista.
The system should be evacuated first (removal of non-condensable gases), then a drop test (checking system integrity) for a certain lenght of time. Then the system needs to be re-filled with the correct amount of R-12, and copmressor oil. The last thing would be a leak check (with a/c system pressed up) with halo torch, or refrigerant leak detector. This should all be done by a professional a/c mech. fuddy has posted articles in detail about automotive a/c.