I am sure you can find something that is close to what you need , on the DLS.
I would start with making the terrain .
Download mapmaker somewhere , and read the instructions ; use google earth for making the maps .
Later on , learn the basics of gmax, and you can build the correct product and rolling stock .
As a steamlocomotive is much more complex to build than the rest , use the one that you have found , but change the textures to something that resembles more what you need.