Using your P2 screwdriver (long), remove three screws from the metal trim which contained the radio. There are two at the bottom left and right corner, and one in the rear, low center of the trim.
Using your panel tool or flathead, slide it between on top of the metal trim and the plastic center stack . Move it gently from side to side, until you hear the release clips click. There are two such clips. Make sure to pull on the trim as you are releasing the clips, and it will slide right out.
You can now replace the antenna plug, have access to the harness and do all your own wiring from here on out.
Install your new ________________, and follow the instructions in reverse to re-assemble the dash. Now enjoy the fruits of your labor,
, and make sure to bring me a tip/lunch/drink when you're in Porter Ranch, Los Angeles.