RO-CK you are indeed a brave soul! Hope that your installation works out with what you have on-hand, but looking at the part numbers on Realoem, are you sure you got the right equipment mount? If you're trying to upgrade to the "Navigation system Professional", then it looks like the 51459193776 part number would fit the bill and not 51459193777? I find part number 51459193777 somewhat suspect because it is appropriate for so many different configurations. Then again I'm a novice when it comes to reading and interpreting realoem part descriptions.
One interesting tidbit I noticed from your photos is that the CD/DVD drive is an Alpine unit. I was under the impression that the stereo was made by Harman Kardon...