Blower motor rattles

I have a 98 Jimmy 120000kms on it and the blower motor rattles and squeaks when heater control selector switch is on position 1, especially on 2 and slightly gets quieter on position 3 and 4(blower motor full speed). This
rattling is driving me crazy because wife drives it and I get all the complaints. I've looked under the hood to see how to change blower motor but the unit is sealed into a plastic factory housing . With previous GM vehicles I've owned changing blower motor was never a problem and with the last GM vehicle I had the same squeak and rattling and it turned out to be a bad ground on blower. Can anyone offer any help on how to change blower unit or maybe I have to grease a bearing or something? Thanks Sam

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