I just started playing Ultima VI and when I did the DOS setup step, I said I had a mouse. I am now considering going back to the text only based interface. If I start up the launcher and choose the DOS setup option, will the game I have played so far be preserved, so that I can resume it after starting the game? Also, will the set of icons at the bottom left of the playing screen go away and will it make room for the map to be a little bigger?

I don't think the icons go away. Your game should be preserved, but I'd make a copy just in case.

After playing Ultima VI for several weeks, I have gotten used to the differences in the user interface and the seamless boundaries between the overworld and the towns. The battles are a little more complicated, since the map isn't as large as the range of the bows and crossbows. But now that I have gotten used to this and begun to figure out how to best deploy my forces, I am really liking the game. I especially like the number of subplots and the fact that some of the subplots are kind of noir. It really has a feel of realism. There are some downright creepy characters in the game!