You have to have ALOT of patience and be prepared to do ALOT of trial-and-error type work. There are a couple of docs on the FARC (link at top of this page) that give some good basic info on the shape file, but they are incomplete so you must try to fill in the blanks. I have a degree in software engineering (its only an associates degree from '93 mind you) and the shape file format confuses me most of the time. Simple shapes like the mule are pretty straight forward, but once you get into aircraft shapes with multiple LOD models and animated textures and polys (like flaps and airbrakes) things get much more complex! CAG has done the most with shape editing in FA so he is the man to ask if you have questions.
