There are two ways to recharge a hermetic unit. The cheap way is to use a saddle valve and squirt in some refrigerant. The problem with saddle valves is they will leak and you will add more refrigerant.
The proper way is to use a saddle valve to open the system and pull the refrigerant out. The system needs to be leak checked and repaired. To properly repair a leak, the systems needs to be purged with nitrogen while the repair is being soldered and Schrader valves soldered in on the compressor inlet and the compressor outlet. Next, the system is vacuum dehydrated to get the nitrogen and any moisture out and checked to see that the leak is fixed under a vacuum. The system is then recharged with refrigerant.
Depending on the capabilities of the technician, this can take 2 to 4 hours.
So if you have an A/C tech buddy, he can do it for you.
Ken