Just in the process of this. The grey panel is simply force fit into place. It is essentially stiff carpeting. Simply bend it a bit to pull it free from the top. To remove the antenna - just a few bolts and plugs.

I sent mine to Becker in NJ for rehab - $120 for a re-build. I'll know in a couple of days how good it works. I also had an I-Pod jack fitted to the radio since I did not want to attempt to change out the factory radio setup and mess with the alarm system.