Everything you mentioned is possible and doable but it is an ongoing process that has taken place over a long period of time. It would be impossible to answer all your questions in one post. The answaer is Yes to all of the above but you're going to have to do your homework and read/google the threads you need and the answers you want.
Best I can do. Maybe someone else can do better.
First of all, I would suggest keeping your wifi off until absolutely necessary in order to minimize your chances of catching the update. Once you're ready to enable the sideloading feature go here --> http://www.google.com/search?q=Nook+Tablet+lilliputing+%22How+to+Sideload+Apps%22&client=safari&rls=en&oe=UTF-8&oq=Nook+Tablet+lilliputing+%22How+to+Sideload+Apps%22&aq=f&aqi=&aql=&gs_sm=e&gs_upl=3168l15548l0l15751l48l45l0l35l3l0l209l1175l5.4.1l10l0. and click on the first result. It should take you to an article with simple directions. If it doesn't, try the cached version. (A direct link to the article kept telling me that the page couldn't be found, but approaching it through Google seems to work.) When the update hits, you won't be able to install apps from any place other than B&N's store, but the ones you've already installed from other places will continue to work. You just won't be able to update them.