Even a 4 year old could wortk this out:
7" http://www.mp3car.com/store/product_...products_id=39 (Xenarc)
8" http://www.mp3car.com/store/product_...products_id=55 (Xenarc)
Also it is possible to add autopower on to the 7" and 8" lilliput screen. See here: Auto Power On 619 Lilliput - Programing Guide
However the 7" lilliput doesnt normally come with auto input on but the 8" might.
I suggest you a bit as it is always useful to know every little detail and issue with the hardware you buy. The general consensus though is that if you are buying a screen to take apart and mold in get a Xenarc if its a 7" due to build quality of the Xernarc brand but for 8" the lilliput is supposed to be pretty good too. Just make sure you get the 800x600 native one.
EDIT: I changed to auto input not auto on (see bold above)