Ok, so I had a little progress...
After holding in the reset button for a few seconds while driving, then letting it boot up and go black, and waiting a while and pressing the eject and map buttons (no particular sequence), I got the screen to come back on again. This time I dug around in the settings, and I noticed that the "Backup Camera" was not set to yes or no. I don't have a camera installed, so I selected No.
That seemed to solve the main issue with the screen going black. It wasn't until sometime later, after restarting the car several times to make sure it was really workin