Check the FAQ for lots of info.
First if you want touch screen for a carputer you wont get it with that system. It may have video input but then you would need your carputer to have video out (not to be confused with VGA out) And the touch screen probably only controlls the unit itself and not a carputer system.
Check mp3car.com store for touch screen monitors. You will find xenarc and liliput screens are common to most mp3car users.
ebay do a search for "car touch screen" or "VGA touch screen" VGA will give you better video. Standard composite NTSC Video (commonly mis-called RCA video) does not look good from a carputer to 7 inch display.
If you want to spend some real money you could try this
http://store.mp3car.com/ProductDetai...Code=SDK%2D007
Search around the site some more before you start buying things.
Plan everything out. It may cost some money. But much less then if you just start buying random crap that you wont need, or underpowered.
Probably want to plan for: LCD screen(VGA), Good power supply based on how much your system draws, how much processor power you will need to do what you want(ie video games music gps internet phone fm camera etc) dvd needs about 1ghz to run smooth, Controll(be it touch screen, mouse, keyboard), and then turn on/shutdown controller(if disired)
Hope this helps a little.