What brand monitors do you have or looking at? They sell kit so you can install them in the seats, but depending on the brand the kits would install differnt ways. Like my clarions they install two differnt ways, If you look at the pics of my old Explorer and the one above in my Expedition, you can see that they are complety set up differntly but install in a simular fashion...
The main steps that would apply to al the setups would be to place the mounting kit up to the seat so you can determine the exact place you want the tv to be. Then you would mark at each corner to start your cuts. After you have your marks you will cut from one corner arcoss to the other to make an X. At this point this is where it determines on how your ket installs. My kit has a instert like in the pic that shows the tv and stuff sitting on the table on my cardomain page (Link in my sig).. Their was an outer ring that wasnt shown in the pics, but I put that behind the vainale of the seat after I removered some of the phome paddig from the vainale, then put the mounting plate intheir useing the vainale wraped around the ring to give it a realy tight fit and hold the mount in place. OOPS before I get to much futher Ofcourse you need to get your wires run though the seat after you get you cuts done, The best thing that you can use would be a coat hanger. After the mount has been placed in you just conect the wires and place in the tv, All done...
Depending on what type of units you run depends on what kind of extra units that you would need to get your multimedia system to run..
Hope that helps explain the install, if you anyother questions let me know.....
Bobby