If the compressor is bad order the Nissens, not UAC or GPD. If you are getting rid of the car just put cheap parts in it. If youre keeping it, get something that will last.
As others said, it’s an AC system, not just a compressor. Have the system inspected and pressure tested to see what the issue really is.
There are easy ways to check if the compressor is engaging. Look down in your engine bay at the compressor and set up your phone to record it operating. Start the car, turn the AC on then off, in then off. Watch the video and see if you can tell if the clutch is engaging and spinning the outermost pulley. If the magnetic clutch is clicking and the wheel is not moving, likely the compressor.
I just had my AC system totally replaced on a 2003 BMW. Parts were $800 and install from a local trusted mechanic (HCOL area) was $820. I would have done it myself but didn’t want to mess with taking off all the lines and cleaning them. So nice to have AC again during this heat wave.