Woot! The 16 gigabytes of memory [1] arrived! It's been installed and it's working beautifully. I'm currently backing up the Mac mini [2] and when I work up enough courage, I'll do an incremental backup in the hopes that it takes longer than my courage holds up, then wait a bit more and eventually, the incremental backup will be over so quickly I'll have nothing left to do but update to El Presidente de Por Vida [3].
Wish me luck.