Append the materials into an existing file, or use the included .blend file as a base for a new file.
https://blender.stackexchange.com/questions/55943/how-do-i-copy-material-from-one-blend-file-to-another

The file also includes custom nodes for layering clouds, city night light effects (Works best in Eevee), craters, and  atmospheres. 

Delete the custom node and replace it with a new one of the same name. It will automatically have the default node values.

Possible? Definitely. Recommended? Probably not, at least not on the the more complex nodes, unless you have a very powerful system. 

You can bake the individual maps, or combined maps to a single texture, in the Cycles render engine.

Blender Docs (Bake): https://docs.blender.org/manual/en/latest/render/cycles/baking.html Video Tutorial (UV Unwrap + Bake): https://www.youtube.com/watch?v=c2ut0Trcdi0

Blender Docs (Bake): https://docs.blender.org/manual/en/latest/render/cycles/baking.html 

Video Tutorial (UV Unwrap + Bake): https://www.youtube.com/watch?v=c2ut0Trcdi0 

https://docs.blender.org/manual/en/latest/render/cycles/baking.html

https://www.youtube.com/watch?v=c2ut0Trcdi0