My old Xplod had a crappy reception but hey thats sony and car audio mixed together.
As Juspimpin said above, there is a plug behind the glove box that comes undone. Simply lower the glove box and it should be right behind it.
all you have to do is pull the thing to the side and it should fall down so you can get acces to the wire
The plug is right behind the glove box and no you dont need to remove the glove box as shown in the pic.. the wire wrapped in foam is the one you need. I assume yours is disconnected.