If you read the thread on the n2a cards, you will get more information. Short answer, no you won't be able to read Kindle for PC books on the Nook unless you root it or buy or create a boot card (ie n2a). In the past for my son's NT we used a purchased n2a card and it worked beautifully. However, many people feel that the n2a people are making money using someone else's hard work (a valid point) and point toward the XDA site which has directions to make your own. For me, that's where I am stuck right now, b/c I have no experience with the most basic coding stuff to understand their instructions. I am hoping to learn. you might look at the XDA site and have no problem following it.
The other option if you are not looking for a complete Android experience but only want to read Kindle books, is to use Calibre and some plugins (Apprentice Alf is your friend) to remove DRM and convert those books to epub and sideload them. No specifics given b/c of the grey legal area you enter, but AA can help.
p.s. I definitely recommend getting Calibre no matter what. It's great for organizing your books and it's free! It's not hard to use, at least at the basic level, although there is a lot more it can do that I haven't learned yet!