I have a Simple Touch w/out Glo, so it's not exactly the same, but I'm happy with how sturdy the unit is. It's in a faux leather case, and I've dropped it, tossed it across the room onto the couch, etc. and it's fine. Don't throw it off buildings or into walls and you'd probably be fine.
I do hear the Glo-film on the screen of the Glo units is fragile, though I can't speak from experience there.
As for converting Kindle books for the Nook, I do it all the time with Calibre. It's super easy, you just have to make sure your books are DRM-free first (Google Apprentice Alf if you have questions there).
Good luck making your decision.