do I need to replace compressor?

Have your AC system checked as it might just be the compressor clutch itself is failing and the squeal is coming from the drive belt slipping when the AC is engaging , You can locate a shop near you here www.repairpal.com/directory

Chevy vents are designed to be a perfect mouse house, they always build it near the heater blower and you have to weasel out the blower housing by prying up the unidash under the glove box, after removing the screws (make sure it is in the off position).