I used 6.5 inch screens. I think that 6.5 is the biggest size that will fit in the headrests. It wasn't extremely difficult but you have to be a little handy when attempting to do it. The toughest part was the headrest because there is no room for error. You can find the screens for about $150 each. I would recommend trying to find the smallest dvd player you can get your hands on if you intend to put it in the glovebox. I couldn't think of anywhere else practical to put it. I got all my stuff at Fry's electronics. You also need a signal amplifier to split the signal to all those screens, otherwise the picture degenerates. Good luck. Write if you have anymore questions. Oh by the way, use a hot glue gun to mount the bezel for the screens to the headrest. We tried using screws first but there was nothing for them to grab to inside the headrest and they started to come loose after a few weeks.