I would look at these two things first since you mention the AC and Stall together.
1. The AC Compressor is working to hard due to low pressure in the system. (if it is constantly kicking on and off and cycling the AC solenoid this can cause your car to stall.)
2. The AC Compressor Clutch or Compressor is failing and causing the pulley to lock up. (this can definitely cause your car to stall.)
The first is the most likely as the system gets older it can develop leaks that cause a need for an AC Service. The second happens when you don't get a service and allow it to continue causing issues or running low on oil in the system.
Usually you can get a purge and fill for around 100.00 they will usually hit it with dye in the fill so they can use a blacklight to check for leaks this will also relube the system.