If you want to get into 3d modelling, my best advice is to download Blender (it's free! Yay!

), and learn/teach yourself to use it. People use to say Blender was difficult to use, and it was a little bit when i first got it. Default control scheme felt like it was set up for a left handed mouse config. But you could change that in the setup menus. Current versions of Blender are much more user friendly.
There's thousands of Blender tutorials on Youtube, ranging from beginner basics to real advanced stuff. So you can easily find what you're looking for. Plus there's also loads of resources out there that will work in it. Textures, PBR materials, HDRI's and skyboxes, complete models etc.
And it's a much better program for modelling than SketchUp.
I'm sure someone out there could likely make a fictional point to point mod road course happen.