If you don't like the nook, and you don't feel very confident that you could root it successfully(especially if you don't have a micro SD, since I'm a fan of not spending money unless you absolutely have to) I'd say send it back and get something that will do what you want it to do, either multi-purpose tablet, or a different ebook reader (be it LCD or E-ink)
into what seems to be an age-old debate, because I just can't leave things alone without poking them....
e-ink screens, while wonderful with battery life, cool to look at, and full of shiny new technology, seem to me to be quite a bit more fragile, and are definately a bit irritating with the way they change. LCDs are, for me, faster, prettier, sturdier, and more versatile.
speaking only from personal experience, I spend anywhere from 10 to 16 hours daily in front of computer screens, and unless I'm uncommonly short on sleep(the 2-3 hours range), I can honestly say I've never experienced eye strain. granted, I do wear glasses, but I have been wearing them most of my life, and they're not likely to have been caused by glowing screens. That said, I do use the night setting on my text, which is supposed to reduce eye strain.
Of course, everyone is entitled to their own preference and opinion, and I accept that some people's eyes maybe even more sensitive to light than mine.
(apologies for the long post, I ramble in the wee hours of the morning)