Building a van isn't difficult in either 3,4 or 7mm to be honest. Stick the sides around a base and that's it.
Parkside generously include both instructions and an exploded diagram in with this kit. I like pictures so guess which one I went for?
One odd-ball is that if you do things properly, the body is built before the chassis. However, the ends of this fit into the recess in the bufferbeam backs. I suppose you could bend the solebars to do this, although I wouldn't fancy your chances. I had to trim them a bit even with my reversed build!