Alleymad95GT is correct on removing the radio. I use Pioneer head units, and they have small metal tabs that slide in on either side of the unit. Of course, I had to remove the plastic trim around the head unit itself. On Pioneers, the plastic trim easily pops off; not sure about a Panasonic.
To remove the head unit, you should not need to remove the plastic trim that Adam95GT is talking about. But if you can't remove the radio any other way, you may have to. He did miss a few screws, however:
There should be one screw at the bottom of the radio trim piece, now visible when you remove the plastic trim around the shifter. The second screw that Adam mentions is only visible way back inside the dash when you remove the bottom din/storage tray. After removing the storage tray, there's a long plastic bar that sits right under the radio. Follow it all the way to the back, and you'll see one screw holding the plastic bar to the dash frame.
There are two screws in front and above the storage tray, just out of sight. You can get to the screws without removing the storage tray, they're on the outside.
The rest of the radio/HVAC trim is held in by metal clips that come loose when you pull on it.