You could do it without scripting by imaging and copying a pre-made image with everything setup as OP has it, then duplicating it with one of these bad boys. Still would require manual assembly and someway of injecting WiFi password.

Raspberries are annoying as heck to log-in too without networking, but you could launch a gui application when you connect it to a computer that then writes the Wifi password back to /etc/network/interfaces so when it gets plugged into the car it can connect to your wifi and provide a http website so that you can check on its status, configure settings, etc