I realize there is already a how-to on this but I was already doing it and figured I would try to take some better pictures for those who need it. Also, thanks to my girlfriend for her hands in the pictures.
Things you need:
T25 Torx Bit Screwdriver
Flat Head Screwdriver
Replacement Antenna Base (Part Number: XS8Z-18919-AA)
Car cleaner (optional)
Car wax (optional)
Get together all the supplies you need. The car cleaner and wax is up to you if you want to get the part of the car underneath the base cleaned up and protected.
Insert your flat head screwdriver into the side of the overhead light closet to the window. There's a little grove to put it in. Just use your screwdriver and ease that side out. From there, just grab the overhead light with your hand and get it the rest of the way out.
This is what you should have at this point. Just unplug the two wires that are attached.
Use your phillips screwdriver to remove the two screws that are shown above. This will allow you to remove the plastic border of the overhead light area. Once removed there is a metal bar in there that can be pushed aside if needed.
Use your T25 Torx Bit Screwdriver and remove the screw shown above when attaches the antenna base to the car/ antenna cable. There is a washer on the screw so be careful when removing as you need that. Here's a picture of it.
Now just pull of the old antenna base and this is what you should get.
Clean the area with your car cleaner and then put a coat of wax on the area.
Place the new antenna base in the holes and get it lined up. Screw the T25 screw and washer back in while making sure the antenna cable gets attached.
Reassemble it in reverse order.