My advice would be:
1) spend at least 6 hours on this board and it's sister (www.replacement-windows.com
) reading old posts and using the search engine to find posts on any term or window product you don't understand
2) ask friends/family in your area for a window company they've used and felt they got a good value from
3) Use the "request a quote" feature available on this site to get in touch with a qualified contractor
4) after you get a few estimates, spend another 6+ hours persuing this site and any others you can find. After that you may be know enough to make a good decision.
Or, you can skip all this and take a chance that whoever you go with does a good job with a quality product at a fair price. Without doing the research it is very tough to know, though.