OK, so I unhide the AppData folder and find the "Mods - 1.191" directory.  Download the 1.191 reference files someone helpfully uploaded to FilePlanet.  Create a "01 - First Mod" subdirectory under Mods - 1.191.  Create a  "GameInfo" subdirector under "01- First Mod".  Copy the entity files into "GameInfo".  Hack the entity files.  Load the game.  Go to Options / Mods.  "01- First Mod" is listed as an available mod.  Click on enable mod.  Lists a checksum and game does NOT crash (as it did when I tried to enable a mod based on reference files for an earlier version of the game).  I click on the "load mod on startup" button.  It lights up green.  Exit game.  Restart game.  Create a new game.  The hacked values do not show up - the original values remain.

What am I missing?  Do I need to create all the other directories under "01- First Mod" (such as mesh) and copy all those files into their respective subdirectories even though I am not making any changes to those files?

Much thanks for any suggestions.