Hey Enrique,
Welcome to IIS
Using a DSLR is the best way to start this hobby, that's how I started out! The D300s is a good camera as well, you should get some nice images from there. To answer your points (Mostly re-iteration of the replies above):
1. Basic equipment would be a tripod, and that's it. If you were using a wide angle lens (Wider than 35mm for full frame, or ~22mm for the DX sensors i.e. what the D300s has), then you would start to notice the stars streaking around the 10-15sec shutter speed mark. If you were using a longer focal length lens, like a 50mm, then this would be in the order of a few seconds. That's why alot of us eventually use some sort of star-tracking mount, whether it be a simple Vixen Polaris or a fully-fledged HEQ5 mount as Danny suggested.
Also Jarrod has made an excellent point, a remote shutter release cable makes life SO much better. I bought one from ebay for my D800, where you can fully program shutter speeds and number of images etc. I could have bought a genuine nikon model but that would have costed a fortune.
2. With the settings, the most important point is your location - dark skies make a HUGE difference to how good your image turns out. A simple drive 30min away from your town will go a long way. After that, you have to experiment with which combination of ISO, shutter and aperature gives you the best result. High ISO will give you noise, Long shutter will give you streaking/trailing stars and a large aperature (>f/4) will distort the stars on the edge of the image.
Start off with ISO 3200, 10sec and f/3.5 with the widest lens you have, and go from there. Have a look in our nightscape gallery section (
http://www.iceinspace.com.au/forum/f...splay.php?f=49), lots and lots of images with DSLRs and the settings then used.
Just remember, the more you image, the more experience and better your photos! And share them with us in our beginners gallery section (
http://www.iceinspace.com.au/forum/f...splay.php?f=46), lots of constructive feedback will be given!