Unless you like tinkering, and possibly cleaning up a bricked device [yes, some people LIKE fixing things they broke. Not me], I'd stay away from rooting.
As to what types of files it will play, according to the BN.com website, it does NOT support .avi, which I was kind of surprised at. My old 'super'pad knockoff plays .avi, and it is a piece of trash.
NookHD+ does support:
MP4, 3GP, WEBM
at least according to the website.