Photography: Where do i start?

So a really good friend of mine used to take lots of beautiful pictures all the time. He recently passed away (he was sick for a while) and his parents gave me his Nikon D7000. Its been collecting dust for a while but i've decided id like to pick up photography as a serious hobby, and what better way then with this beautiful camera. I've always loved taking pictures but never had the money for a serious camera. Now upgrading from a point and shoot fully automatic to this type of DSLR is something id have to adjust to. I know the terminology and they technical aspects of SLR (i've played with some in the past) but i'm having difficulty actually putting them into application. When i take good shot i feel like its by fluke because i don't know how this photo turned out good.

My question is, for someone new to DSLRs where should i start? Is there a book i can read that'll help? Or should i take a class or are there really good you tube instructional videos? How do i adjust the aperture, depth of field, ISO, etc to achieve great crisp shots. ( :P not literally "how" but more so in "what circumstances") Anything would be helpful thank you.

Also, I love nigh time photography, nature and portrait, and i have a 18-200mm lens that i got with the camera.

Take a class in basic photography. You have an excellent camera, but now you have to learn how to use it to get the most out of it.

The 18-200 mm lens is an excellent single lens solution

You seem to want to jump in to the deep end of the pool without taking lessons. Slow down and breathe. NO one became a competent photographer over night. Plan on spending a few years learning how to use your camera, see lighting and producing well composed images

There are free videos here that will help you understand http://www.mccordall.com/photography/ well worth a look and there are some for the beginner.