Your original Nav DVD should be in the hidden DVD slot which you get to by pressing the button "tilt" on the lower right side next to the Nav screen. After about 3 seconds the DVD will appear. Take that out and you can put in a DVD movie and play it. You can't play a movie while driving, only in park. There is a code to do this but it's to involved and would not be prudent of me to post that code because of the danger of driving while a passenger was watching a movie and you glanced at the screen. Others may offer it to you, but I can't.
The slot on the face below the nav screen is for your 6 CD changer that you can load up.
To get you started until probably Bruce, our tech, who will probably tell you where to get the nav DVD booklet, press the CD button and you can see 6 places to load the CD's. Press the first space which will light up blue and follow instructions for loading the CD's.
If you didn't get the DVD, OnStar manual, or the instruction manual for the DVD, you need to go to the dealer and inform them that you are missing these invaluable documents that initially came with the vehicle and is part of the vehicle. It should be no cost to you.
I hope you where trying to put a DVD into the slot below the nav screen which was the wrong slot and their is nothing jammed in your hidden DVD slot.
Have a Happy Easter