You can't really check the refrigerant. There's special ports under the hood to hook up to and add fluid. What's your A/C doing?
Ok, I finally have more information. We found the port and attached a meter to check whether there was a need to add refrigerant. The meter indicated that the pressure in the system was over 140 psi - thus there was no need to add refrigerant. However, the a/c still doesn't work. There is no "drag" feeling on the engine like there used to be when I turned on the a/c and there is no sound of the "motor" or whatever turns on when I switch on the a/c. Does anyone have any ideas as to what else we could check.
There are two sides to the system, a low and high side. You are supposed to hook up to the system and start the car, turn the A/C on and see if the pressures change. If not then the compressor isn't on. So if you look down at the back of the compressor there's an electrical connector that goes to it, unhook that and give the compressor 12v power from the battery and see if it turns on. If not then you need an A/C compressor. If it does turn on listen for weird noises and also watch to see if the low side pressure drops down to about 35 psi and the high side should be around 125 or maybe a bit higher.