It's alot easier to hook up a DVD, Video Game or any sort of system like that in a car than most think. You need a stable power inverter, i hardwired mine in instead of using the cigarette lighter. And as long as you have a monitor that accepts some sort of Aux input you're good. On mine i had to run the Aux inputs into a DVD player i put in the Rear between the seats so that i hook my Xbox 360 into the RCA inputs. Just remember if you're hooking it up into a Driver's seat viewable monitor, check you're local laws about having it on. It's not a cheap ticket.
As for the power level of the inverter, Id look for a 800watt with 2 or more outlets on it. I have one with 2 plugs and its great for my 360 and my cell phone charger. I also have mine hard wired to the battery, this way you have a constant voltage and the game system doesnt turn off when you turn your car off like it does with a cigarette lighter plug.