96 GL A/C issue

Hi. I just found out that my A/C has a major problem. I thought it just needed charged but that's not the case. Auto Zone told me it was either the A/C clutch or the compressor. Before I bought a new engine, I remember it making a loud screech sound when I turned it on. Now its not working. When I turn it on now, the RPM's rev up about every 10 seconds and the van jerks a little when at a stand still. I just had the vacuum lines fixed also because it was only blowing through the front defrost. So how can I tell what exactly is wrong? And if its the clutch or compressor, how hard is it to fix or replace? I'm not too experienced with auto repair so most likely I will have to take it in. Thank you!

The symptoms you are describing sounds like it could be just low refrigerant. I would not trust AutoZone to analyze an AC issue.

Raise the hood and observe the ac clutch while the engine is idling with ac "on". If you see that the ac clutch is cycling ... you probably just need additional refrigerant.