Mattm, there are a few things you can do here, now that you've taken the plunge so to speak.
You can spend some time learning DEM and build your self a nice route.
or
You can spend some time learning DEM, build your self a nice route and record your progress as you go. Should you decide to take the first and easiest suggestion of the two, you will join the largest section of the Community by far. You will become yet another one of the the Community who doesn't bother, or doesn't like sharing.
Alternatively, you can run WordPad and IrfanView in the background, taking notes and screenshots as you progress. At a later date, you could then create a tutorial an share it with us all. In doing so, you would become one of the elite and join the Content Creators, Route Builders, Tutorial Writers and Wiki Contributors, all of whom have a special place in the World of Trainz. Without any of these dedicated people, Trainz may not even exist!
If you start from the beginning, the moment you begin downloading the software and report on problems, suggestions, frustrations, even better. No skills are required other than to write down what you do. Of course you can create your own tutorial using HTML or a wonderful little free program called Wink. Alternatively, you can send all the screenshots and your notes to me and I'll create the tutorial for you. That's what Bill69 did and here's the result:
Tutorial Link
You can have it hosted exclusively at the TRD, or at your request, I'll also upload it to the Trainz Wiki, which like the TRD, is trying to keep Trainz on the rails.
If you need any help, please PM me and I'll send you my email address.
John