@dave r said:
I'd start by drawing a plan view as well as a couple of elevation views. If it is easiest, do that on your pad of paper. scan and import as an image into SketchUp. Then trace over the lines to create faces you can extrude and intersect.
There are all sorts of tutorials out there for drawing vehicles. You should search YouTube. I bet you'll find a lot of help that way.
Sadly, I'm at work right now so Youtube is out for a few hours, but I'll definitely check that out when I get home. I kinda got lucky on this sketch though. Never really was too good at drawing things. At least, not at keeping them all proportional and such.