Everything worked in the upgrade process.
I forgot the step to empty the directory templates_c so I received a Smarty template error. Everything seemed to work after that with no error messages.
My goodness, though. Instructions for upgrading are unwritten, and the "upgrade" function of the software itself that displays the cheat sheet for initiating the upgrade only gives one part of the process (doesn't cover at all the config files that must be uploaded prior to the upgrade PHP script.) I don't expect to bother with this for another couple of years with this kind of procedure.
I recommend (1) asking the user to upload the entire unzipped upgrade file to a new specified subdirectory under the public directory. and (2) generate a shell or bash script that performs the copy of the 30 or so scattered files that must be done manually now. (3) instruct the user to go to the command line and execute that script.
Then you'd need less documentation. Or at least eliminate some error prone manual steps.