I can't remember exactly. You could remove the ashtray see if there are any screws up underneath, and try gently prying down on the top of the trim plate as it might have small tabs that hook the underside of the dashboard. I seem to recall the top comes out first.
I removed the whole dash when I had to change the heater core. There are a few control rods for the heater control that have to be disconnected before you can take it out. One for the temp control, one for the mode selector, and one for the inside or outside air. Before you start pulling things apart, you may want to look at all the electrical connectors under the dash and make sure everything is plugged in. I think the heater control has a plug that connects to the wiring harness in the dash.