'72 C-10 AC Compressor Clutch smoking. Help!!

[VAPhil]

Hey everyone,

I'm reading a lot of mixed advice on troubleshooting a compressor problem. I bought the truck a few months ago. Looks like original compressor. During idle, pulley spins & stops occasionally. Recently, when turning the ac on, it squeals loudly. Took the truck home today and i had smoke coming from the openings on the pulley hub front. Air stays cool, never been "cold."

Is this a seizing of the clutch? Low on oil? (Don't know if its R12. Whats that even mean?) Can I repair this myself? i'm relatively ac stupid.