This is another approach to putting electronics into a car on a very tight budget.
A kind donor gave me a broken car DVD player set with 2 nice 7 inch monitors. A bit of re-wiring and they now have simple 5-pin DIN plugs carrying power, video and audio. I then acquired an old VGA-to-Video adaptor that had lost its leads and power supply, but that was easy to sort out and here we have a test bar graph application running from an old laptop. The program was written in C using the OpenGL graphics libraries and runs under DOS.
I've re-created this in Linux, but DOS has a lot going for it in simple applications like this, most of all the fact it runs in RAM so is ideal if you're using a compact flash card as an alternative hard disk drive. Fewer writes to the card the better.