Landscape beginner ...

Landscape gear? I am planning on taking some (probably quite a few) landscape shots for a project. The photos will be mass printed in a format of approx 7,5 cm x 15 cm. And also used for web site backgrounds, but no poster magnifications or anything like that. Would the latest SONY a37 with a  Sigma 10-20mm f/3.5 EX DC HSM Sony-alpha lens be a good idea. I am a beginner so please be patient! I have understood that the lens is a very important part of the setup. And I see that some lenses have a focus motor while others do not. Do I need a focus motor for landscape? And what about fixed aperture? Is that a must? And finally; what should be minimal focal length?

There are two kinds of lenses for Sony Alpha, one DT and the other Full frame. If in the future I upgrade to full frame, then only full frame lenses will fit, right? Thanks all! Open for other ideas ....