245 Compressor clutch about seize???????

1982 245. Air conditioning just re-gassed and blowing very cold. In the last week I have noticed vibration at highway speed (felt like wheels unbalenced), but not really around town. Just checked under the bonnet (hood???) and I notice that when the thermostat engages the compressor there is a grinding noise from the compressor. Once the A/C gets the cabin to the required temp, the clutch at the front of the compressor stops spinning and the grinding noise stops. When the A/C is not engaged there is no grinding noise at all, although there is some belt squeal, which could be poor belt alignment due to hardenend bushes.

The compressor was replaced about 5 years ago by P/O but the invoice shows that the clutch was not replaced at the same time as it was "ok".

Questions: Would a faulty compressor clutch cause a vibration as speed that could be felt in the cabin?. Is replacing the compressor clutch a difficult job? If I do not attend to this urgently is it likely that the clutch could seize causing loss of power steering.

Thanks to all and cheers from a hot Sydney, Aus.