Tom,
If you want to learn -- really learn -- how a prototype wood frame car is built without having to crawl around under a real one then build a San Juan kit. (The proprieter of San Juan, John Parker, is an N scale Rio Grande modeler by the way) Bulding one of these will let you see the how the parts relate to one another on the real thing.
If the On3 stuff seems a little big, then try an Sn3 kit from P-B-L -- they are essentially the same (many were tooled by the same guy for both outfits) -- and, yes, there are as many pieces on an Sn3 car as there is on the On3 versions . . .
Good luck, and be sure to share the results!
Marty