Swordo Posted:

Does the first clue need the use of the Caesar Shift to decode it?

You mean like a ROT13. No. But good try there.

zagerblag Posted:

Is it a physical reference guide, a virtual one, the phrase “a reference guide” or some variant thereof, or something else?

It is physical. But like all things you can find it on the internet. And the code is not based on the phrase.