The quick mock-up I did was really simple tbh. I just opened both of the images in photoshop (logo and van pic) and dragged the logo over onto the picture of the van.
Depending on what angle the actual image of the van you'll be using was taken at, you'll probably have to play around with rotatations, sizing, opacity, blending options etc...just so that the logo doesn't look as if its just been stuck on (the logo should follow, and show, the contours of the van picture underneath). I hope that makes sense? Sorry if it doesn't but I've got a killer hangover at the moment and I probably haven't described it in the best detail.