The best place to start is here:
for power supply, you can use either a inverter and a normal power supply, or a dc-dc power supply that usually includes a startup/shutdown controller that would trun the pc on/off with the car.
For cases, I have heard some good things about mo-co-so cases, but anything you got can work. My install is on a small sheet of plexiglass..
For lcd's, from what I have read, stay away from flipout single din screens and try to fita fixxed double din screen. I use a lilliput 629, but lilliput and zenarc both have touch screen models that work great.
Also your might get a little flak for the 4 gb of ram- usually 1-2 is enough for most systems...