Stay FAR away from the Four Seasons compressors. Their quality control is marginal at best. Yes, get the one with the clutch. New is the best way to go.
NEVER EVER use sealer. It will either not work or will totally hose your system. That stuff is pure snake oil.
Along with the compressor, replace the accumulator and orifice tube. Flush the evaporator and condenser and add back the proper amount of oil.

Be sure to pull a hard vacuum before charging. Don't use the cans with the hoses attached, this is just begging to get air into the system. Use a manifold gauge set with a proper can tap.

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