http://www.google.com/search?hl=en&source=hp&q=nook+ebub+support finds this is far from simple to do.
My bet is that any DRM'd epub will fail. In fact http://blog.threepress.org/2009/12/11/nook-as-an-epub-renderer-review/ wrote "Loading failures
I tried loading a number of O'Reilly Media titles that are valid and work on the Sony Reader and every other ePub device. The Nook only brought up the "Formatting" message, and then hung. Only a full restart would bring it back.
This is an extremely serious problem. "
BE SURE YOU ARE NOT EXPECTING THIS TO WORK. If you thought it would and it doesn't, go get your money back!