Everything was a success!
I was already on the latest OS and after the MD was first turned on after the installation it did some very quick maintenance and asked to restart the unit. After that I had the +Drive options. To answer one of my own questions, there is a “Format +Drive” option. So if I feel like killing off all the preloaded kits and patterns then it should be simple.
Some stuff not immediately obvious to a +Drive noob like me. The preloaded snapshots only take up to snapshot 35 or so leaving over 90 blank snapshots. Also, best I can tell, you NEED to save your current MD snapshot from prior to the upgrade to a blank snapshot slot before loading a new snapshot or you will lose everything you had before. I did make sure I got a few good sysex dumps prior to opening the unit, but I did notice this before loading a new snapshot.