Not sure if this will help anyone, but I was curious..
So to remove the "unicorn" antenna, you're going to need to access it from underneath. To do that you need to pull down part of the headliner in the back. The best way I could find to do this, is to stick your fingers under the headliner and get them as close to the plastic fastners as possible (on either side) and pull down.
Once you've got all 4 fastners loose, you'll be able to see the bottom of the antenna:
Now there's 2 wires running to the antenna. The power wire slides off to the left, and the Antenna connector pulls straight down:
Now you'll have to unscrew the nut connector. You'll probably need a wrench to loosen it, after that you can turn it by hand fairly easily.
Here's what the nut looks like:
Now you should be able to pull the base right off. There's some little plastic parts holding it in place, but you should be able to pull it right off without hurting them. Here's what it looks like once it's off:
Once you've got the base off, there's a rubber gromet that just snaps in:
Once you remove the rubber gromet you can see there's 2 screws and some plastic snaps holding the circuit board in:
Once the screws are out, you can remove the board fairly easily:
There's 2 other screws holding the circuit board to the metal part which you can remove, but there's actually a brass part coming from the metal base to the circuit board that is soldered on, so you can't actually remove these parts without removing the solder.
That's it. Hope this helps someone...