Hello and thanks for using JustAnswer.I will try my best to help you with your question.
To remove the radio on your 2008 Edge, you will have to remove the trim panel that surrounds the radio to get to the 4 screws that hold the radio to the dash. It just clips into place around the radio. use and flat blade screwdriver to carefully lift the panel away from the dash to release the clips.
I'll try it tomorrow.
Your welcome. Keep me informed.