Find the fuse for it, and pull it. The owners manual will tell you which fuse it is (or sometime in those old GM's the backside of the fuse box cover has a fuse legend which tells you which one is there. The other more "hands on" approach is to go in the trunk, pull back the liner, and unplug the antennae (if its the antennae is up front, find it under the hood and disconnect it). If you choose the hands on approach make sure you cover the connectors on the wire with electrical tape to ensure they aren't touching other metal thereby causing other electrical system failures and or issues. Best of luck !
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