I have a couple of questions -

When I turn on the car - the ac clutch makes a metal to metal grinding sound - after 5-10 secs or so the noise goes away. I think the AC compressor comes on and the sound goes away. From the inside if I turn OFF the AC the sound is back - If I turn ON the AC again the sound goes away. The AC is cooling fine just the very annoying sound.

What exactly is wrong with my A/C clutch - bearing, etc?

Can I change the clutch only without emptying the AC gas? It is better to change the entire compressor with a rebuild?

Thanks.