If you want to retain the power antenna, I would recommend replacing the unit. New OEM is very pricey. You can always repair one with a good motor and broken mast. Save yourself some money and do it yourself. I probably have one with a good motor and broken mast if you want to go that route.
The other option is going with a fixed mast set up. Not sure if you cover your car in the garage but its a pain with the fixed mast unit.