Trouble with the Themes
So, I was pleasantly surprised to see the "Edit Theme" button in the theme choice window, and I spontaneously clicked the edit to a theme I didn't have installed, I later realized. It showed the theme I /did/ have installed in the preview pane, but it didn't update the preview no matter how many changes I made. (A few attempts at font size changes and a header with an upload).
I ended off by clicking OK, but I got "Internal Server Error". The end result, I am stuck with the theme I was (accidentally) editing, as no other theme can now be selected.