Air Conditioner - Compressor or Clutch Issue

My AC went out yesterday. It is an integral/factory installed AC. Is it the case that with a non-functioning integral AC, you can merely replace it with the same functioning integral AC *or* is it once the integral AC goes bad, you have to resort to a hang-on? I found an integral/factory AC from a salvage yard (it tested fine) and I was curious if replacing the bad with the good is standard. Or if I have to resort to a hang-on. I know my AC is out because it would draw a charge from my battery when I cut it on, and now nothing has happened (no charge draw, no initial labor from my car when the system kicks in). Could be my clutch belt, but how would I know if it were?