If your antenna motor is working all you need to replaced is the ntenna mast. You can buy it for about 35.00 dlls from the dealer. that will do the job.
The link below will take you to the steps by step instructions on how to replace it.
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.