We were all where you are right now, perrybucsdad.
Time patience and experimenting are the biggest part of the package. Trainz isn't your normal "game" and is more like a real model railroad except it doesn't take up any real physical space not counting the cells in an SSD or the ferrous surface sectors on your hard drives. The routes are the layouts and the sessions and what not are the operations. Scripts and other underpinnings are like the wiring to make it all work. Like building a real basement model railroad, you need to focus on a tiny bit at a time and not dive into everything at once. And more importantly, like a model railroad, don't jump in and plan to build the biggest layout, or in our parlance, a route. Start small and plan on scrapping your first routes. This is exactly what I did back in December 2003 a few days after Christmas when I went to CompUSA and got my copy of TRS2004.
I had tried the early demo versions and liked that I could create my own routes and like you I didn't quite know where to begin. I poked around the DLS which at that time was an online affair that required going to the Auran website and then to then black pages, now recently updated to white pages. There I downloaded some trains and some routes which I took a look at. There were a few routes that caught my eye, and I gave them a try. The first route I tried, which I can't even remember what it was called, had a great title but turned out to be crap. The track wasn't seated on the terrain along with other sloppy things that I didn't like. I deleted it and tried another and another until I found one that caught my eye yet again.
I opened this route in Surveyor as I did the others, which really hasn't changed much since then, and poked around to see how the author did things. I noticed that this particular author paid great attention to details and his track was actually tamped to the ground and not hovering above the ground. He had also done the same with roads and other splines. The texturing too was great and so was the tree placement. While in Surveyor, I took the route and added a loop of track off to the side and imitated his texturing and other things the author had done. I was learning from this author how to build a route by poking around, imitating, and experimenting. I did this with a few other routes by other authors and then one day I decided to start my own project.
My project started out as 4 baseboards centered around a port and a passenger terminal. This was based on a model railroad I had planned and partially built back in 1984 but had to be scrapped and then attempted again in 2002-2004 and had to be scrapped due to many reasons which always happens to big model railroads I built. I went about this carefully and used photos and topo maps to get an idea of what I wanted with track layouts. My building skills were crude, and I tried my best to improve them. One of the biggest errors I made which affected the whole early route was I thought by setting the scale in the route description when we create a route would set the actual working scale - it does not as I found my heights to be totally incorrect. My 12-foot difference between levels I wanted, turned out to be more like 39 feet! As time went on and more to the wise, I rebuilt the route but kept that port section which still exists today as part of my current large route project.
In the end, don't be afraid to experiment. You can't break things and the only thing you waste is your time and a few bits on your hard drive.