Set parking brake and disconnect negative battery cable.
Insert DIN tools into holes in each side of factory radio and
gently push into holes about one inch until a click is heard on
each side. Spread tools apart slightly and pull out radio.
Disconnect wiring harness and unplug antenna lead to remove
radio.
Since you already have the radio out, if you can get an extra set of hands to pull the removal pins apart, you can reach inside and push it out from behind. That's what i had to do and it worked fine.