The a/c compressor clutch in my '96 XJ (4.0L 130K) makes a repetetive chirp as long when it is not engaged (a/c or defrost not on). Could this eventually lock up and become more than a nuisance? Can the clutch be easily replaced without special tools and having to discharge the system? A local yard only sells the compressor and clutch as a unit, which leads me to believe this may not an easy swap.