i really wouldn't bother to be honestyou will need a 12v to 240v inverter which in itself will cause you problems as putting a 240 tv on a 12v system and playing it through your sound system it will give so much interference personally all the money you would spend on the tv,the inverter,al the bracketing it would be probably be cheaper to just buy a proper in car roof mount dvd player this is what i have in my roof plus i have 4 more screens in the car
this particluar one if you can still get it(which i doubt as it ws discontinued a couple of years ago) cost around £400 it has its own built in dvd and aux input for a games console and infra red leds for headphones aswell