Sure it's possible. But is it practical?
You have to ask yourself where you're going to put a 15" monitor in your ride.
Has anyone hacked a LCD Monitor with an internal power supply such as this one to bypass the internal power supply and run 12 vDC?
right in the middle of my dash, i have a quadruple din space to work with
And I agree with malcolm. It very likely requires regulated 12vDC.
Can the AC-DC converter be removed or bypassed? Possibly.
Personally, I think it would be easier to find a touchscreen that uses a "power brick". That power brick handles the AC-DC conversion.
With a setup like that, you can simply provide the proper regulated voltage and call it a day.
I know for a fact that such touchscreens exist. I have worked for companies that resell them.
(Before you ask - no, I don't have a line on them any longer.)
I personally would look for one of the newer ELO's that use the 12V adapter if you are set on something this big. We have several of these units at work and the older ones (like in your link) reflect the sun like a mirror. The newer style ones don't show glare as bad. If I had the amount of space as you I would get a 10.4" screen and use the additional space for a slot load DVD drive.
Anything is possible with some hackery. How good are you at making/figuring out circuits?
My Nearly Complete Car:
Micro Control Center... Control Your Car Across the Internet
Website: (It's a work in progress, really. All my projects have taken me from ever really developing it.)