This is pretty heavy-duty reading for the uninitiated, but has loads of good info...
http://www.fs2x.com/ --> click on the TUTORIALS link
I haven't got my head wrapped around much of it yet, and have gone the route of modifying default gauges to save time, which gives some good results. Manipulating these (even just cosmetic tweaking) opens up how gauges work a lot better than simply reading a pile of documentation - it's like anything, best way to learn is to get your hands right into it. Good luck with your project!