Quick answer for your first question: If you've got a .deck with a font saved (e.g. if you save a copy of the font editor), you should be able to drag it onto the deck you want the font in (like literally drag the file into an open Decker window), and then use the Font/DA mover that pops up to move the new font into your deck. The same goes for moving around different colour palettes, sounds, contraptions, or modules, when you get that far.
Looking at your second point, yes I think that should work - it's pretty easy to write code that hides or shows a widget based on a click