Ok, I gotta say it... DAMN GOOD JOB M8!!!! That looks great, I know its the wrong truck but you did a fantastic job... So I gotta know how you did it, what tools u used?Create a new layer with just the paint able areas and... im barley an amateur at phrotoshop. and trying to better my skilz.. So your input would be greatly appreciated.
Thats for the compliment dude but I am FAR from even close to an expert on PS.. Here is what I did though...
Copied the background layer for editing, made a new layer and went to edit, select color range (on the new layer) edited as much of the color of the truck selection, then I went to the paint bucket and filled it in with whatever color I wanted. The parts I missed I just went around with the paint brush (using the same color) until I got all of the truck painted. It will look like crap at full opacity but you can turn it down and then use the eraser tool to go over the lines of the truck to clean it up.
Once you do that then all you have to do is turn the opacity (on the new layer that has the color selection and color you want all the way back up) then you look above your layers and you will see a drop down box with "normal" selected. You want to change that to overlay and then it will look realistic. If the color is off again you can just go to the solid color only selected layer and go back into the edit, select color range and click it and since the color is all one solid one you can select it easy and then go to the paint color button to change it. you can also adjust that layer by going to adjustments, hue saturation I believe.
Damn its a bltch to explain it and I could show you in like 1 minute if you could see what I see. I hope that kinda explains it to ya. BTW I have only been using PS about 6 months and I don't really use it that often if that helps. I would suggest going to youtube and typing in like "photoshop car color change" and you can get a better idea. Good luck dude