At the very bottom of your center display, there is a long, narrow black panel with an opening on the left side. You need to stick a small screwdriver or paperclip in there and pry the panel up so that it comes off.
Once off, it will reveal a small, round black button on the extreme right side. When you push that button, the Nav Disc will eject.
When you are done whatever you have to do and the disc is back in, the long, thin black panel will snap back into place.
The DVD slot has an access cover over it and is located immediately below the display screen. With a small screwdriver, paperclip, etc, press down on the little tab on the left side of the cover, then pull the cover straight away from the radio. Behind the cover, on the right side, is an eject button. Press the button and the DVD will come out.