They put in a new motherboard, and now all is well.  Oddly enough, my Office365 subscription got mangled, but I un- and re-installed it, and it reactivated just fine.
The Dell program that keeps tracks of updates popped up this morning and said that there were two important updates available.  One said it downloaded and installed just fine. Then it wanted to do the BIOS update, so I let it reboot. After going through several progress bars (BIOS, Intel Management Engine, ...), a green message with a check mark came up, saying the update was complete, and that the system would restart.  A few seconds later, the screen went black, and nothing else (visible) happened. The power never went out (it's on a UPS anyway), and I didn't interrupt the process. The power light is now flashing 2 amber, a pause, and then 6 white -- "System Board Failure". I MUST get this system back online quickly.  What do I have to do to have a motherboard dispatched for replacement ASAP?
Precision 5830 bricked by BIOS Upgrade