I got an HDMI cable today, and have the JMRI home page displaying on my monitor! The USB mouse works, too.? :--)
I suppose I'll need a keyboard connected to the Pi to configure it to connect to the router, at least. I'm debating whether to borrow the one from our primary computer, or spend the $20 or so to get another wireless keyboard and mouse for it. It they could serve as backups to the ones on our primary computer, too.
It's beastly hot here this afternoon, and the car is out baking in the hot sun. I think I'll read Steve's documentation for a while first!