I have done something similar, so I might be able to help.
My folks 07 MADP came with the GARBAGE VDO "car-in" nav system. I have never seen another newmar with this particular unit. Honestly the UI was so awful it was unusable.
They had a single LCD display that similar to yours was shared by the cameras and NAV. They had a separate double DIN stereo/CD/XM system.
What I did was remove the nav system, its DVD-Rom drive took up a single din slot, and removed the stereo.
I replaced the double din stereo with a fold out LCD to be used for a 4th dedicated camera (installed in the dingy).
I added a single din Alpine ipod unit within the former location of the DVD-Rom drive.
For navigation I got a stand alone Garmin unit (660). The reason I used a stand alone is ease of use, and upgradeability. With the speed of innovation within the GPS market, you most likely will want to upgrade in a couple of years. (if you want to get geeky with GPS chipsets we can take this offline, I don't want to bored people to death here)
I have played with most all of the "built in" nav systems. Pioneer makes a nice setup, but its UI still could use some work. All of them are grossly overpriced.
For the price of a double din navigation system you are looking >$700, add on a xm tuner, or ipod interface and it can climb to over a grand.
As a comparison you can get a top of the line in dash stereo (no nav) for less than $450 (ipod/xm/sirus/hd radio)
Now a warning about installing anything in the dash. Unless the King Aire is completely different the dash is comprised of molded plastic, with "plastic rainforest" wood finish.
This "wood" is extremely fragile. I have had the entire dash apart, and its rigidity leaves much to be desired.
I would not trust it to a car stereo shop. Nothing against their work quality, but to the fact that even a pro will damage something. It is that fragile.
This photo was taken during the installation. The garmin nav sits on the left side of the dash in its own holder. So while driving there are 3 separate screens. Nav on the left, rear/L/R cameras in the center, and the dingy cam on the right. No more switching between video sources.
Now for better sound.
Above the drivers area were two compartments that contained separate cube speakers for the "home theater" system, and a separate cube setup for the dash stereo. Both were garbage, and in-fact the speakers were so poorly secured I am surprised no one was hurt with them falling out.
I removed both sets of speakers and created my own ported cabinet. With some simple wood working tools I used MDF to create a proper speaker cabinet within the existing cabinet.
After properly damping the inside of the cabinet (using dynamat) I mounted a pair of JBL 3 way 6x9's.
Finally I removed the louvers on the cabinet cover (held in with wood staples) and replaced it with some high quality speaker grill cloth.
So far no one has noticed it isn't factory.
Even though I only power it via the new in dash stereo, I can POUND out the tunes if so desired. It is a monumental improvement to what was there.
All said and done I have about $150 into the new speaker setup.
Here is a photo of the finished speaker cabinet. Sorry I do not have handy photos of the speaker setup install. The tweeters are only visible because of the camera flash.