I installed CM10.1 on SD cards on both the HD+s I bought in the past few weeks using verygreen's straightforward instructions at
http://forum.xda-developers.com/show....php?t=2087988 He also provides a link to the latest version of ClockworkMod (7.1) and instructions on how to use it.
Also,there is a FAQ about the basics of rooting at
http://forum.xda-developers.com/show....php?t=2317500
If B&N is really getting out of the tablet hardware business it's important know how to root Nooks so system updates are available.