Depending on if your car has a power antenna or not, you may have to replace the whole unit.
The good news is, no, you usually don't have to replace the wires on most GM vehicles. Open your trunk, remove the insulating carpet from the side of the trunk where your antenna is located , to expose the power antenna unit.
This is a stock photo of what the power antenna unit and kit looks likes.
Unplug the electrical connector from the antenna . Unscrew the plastic ring on the outside of the car, where the antenna rest on the body of the vehicle. Pull the antenna unit inside through the hole to remove.
You can usually get a new one for about $89 bucks at Autozone.
Installation is the reverse of remove. Make sure the ignition key is completely off when performing the replacement. Follow all installation instruction on the package. Improper installation could cause rain to leak in your antenna during bad weather and not be water tight.