The only way I can ever figure out what I want to do to a vehicle is to do a couple of renderings. That way it gives me a quick idea of what will look good and what I need to avoid. The renderings don't even need to be perfect at first, just load a pic of the truck in to Microsoft Paint and start coloring what you think you like. Once you have a general idea then you can either pay someone to do a finished one ( Only do this if you are planing on doing a lot of changes and want a "Game Plan"), or download a free rendering software and make it yourself. I personalty use Inkscape and Sketchbook Pro for my customers or my own renderings and they all start with a simple Paint image.