So far, I haven't managed to break anything, although I did mapserve once partway through the process on Saturday. I was glad to see, when I logged back in, that all the changes up to the mapserve had remained, nothing lost in effort.
I'm amazed at how fast the base-building tool skills have come back, wow! My project, a pub, isn't as ambitious as a lot of the bases folks are working on, but I'm using millions of bookcases to build walls, and getting fancy with "clipping" items together and submerging things into the floor, for things like the fireplace. (Bless that SHIFT key!)