You should be able to do the softroot exactly as described here
http://nookdevs.com/Softroot. Please follow this page, you do not need the other softrooting. It means you will first downgrade to 1.0, then upgrade to the nookdevs rom 2.5.1, which should show as 1.5.0 in your nook. Afterwards your nook will probably upgrade on its own to 1.7.0, which is the current fw, and you can let it do it, you will stay rooted.