If you go to a big bookstore, you find for any of a number of commercial, complicated software programs, books entitled "The >Software< Bible", or similar, which tells you all you need to know, and probably then some, about the particular title. As far as I know, "The Trainz Bible" has yet to be written. However, I'd recommend that the first place to start learning about creating content is on Auran's website, specifically at <http://www.auran.com/TRS2006/public.page.php?location=downloads_learning_centre>
ns