This is a great series:
Scott Kelby's Digital Photography Boxed Set, Parts 1, 2, 3, and 4: Scott Kelby: 9780321839954: Amazon.com: Books
He states outright, without apology, that it is not about the science of photography, but instead if you and he went out on a shoot together and asked what would be the best settings, he'd say "Set this to this, that to that, and take the pic", as if you were a friend out hiking with him.
Check out these forums:
https://www.nikonians.org/
Nikonites - Nikon Photography Forum
Both very informative and very friendly
An online site you may want to check out for general digital info:
Photo Class | Mountain Adventure Photography
I reluctantly finally made the jump to digital from film just last year and went with a D5100 and love it...I know you don't want to shell out extra $$ since just getting the camera, but I'd HIGHLY recommend picking up a nice flash unit and rip the pop-up of the camera
Now, about the tripod and head you want for low light, astrophotography, portraits....etc
Congrats on the new toy!