I am by no means a mechanic, but if you can turn a wrench you can fix that antenna. There is a nylon string inside the antenna that moves it up and down.....over time the nylon breaks and the antenna gets stuck in either the up or down position. I found a rebuild kit on one of the GM online parts stores for around $20. The fender does not get removed, but you do have to take out the fender bolts that are on the inside of the passenger door. After you remove those bolts, you can peel the fender back far enough to stick your arm in there and remove and replace the antenna. Fixing the antenna is a piece of cake that only takes couple of minutes.
The rebuild kit came with instructions for fixing the antenna, and I got directions for removing and replacing it either here or on wwwgnttype.org. Good luck!