Nice choice, hope you take some good pictures!
I noticed you asked about software: Nikon do Capture NX.
It is NOT as powerful as Photoshop but it is sure as hell a lot faster to do anything and a lot easier to learn. Even though I have Photoshop CS, I hardly ever use it, mostly I use Capture NX. It's not that computer resource friendly though (and I don't know if it works on a Mac)... when I installed it, I had to buy more RAM. But first, try to get the picture right in-camera. It's easier, it's faster than postprocessing it to save it later.
Here's some tips, since I'm familiar with the D90
- The default sharpening is quite low; if your pics seem to be not as sharp as you like, adjust the sharpening
- Get to know single point AF, continuous AF and multi-point auto AF
- Get to know your picture controls
Here's a user guide for the D90
http://www.kenrockwell.com/nikon/d90...uide/index.htm