Window frames are either wood, vinyl, aluminum or sometimes different composite materials. Deciding on which material will be right for your home will depend on your particular needs. After you decide what the most important feature (low-cost, energy saving, style, etc.), then you can make an informed decision about what to buy and who to hire for the job.
If you live in an area that gets frigidly cold during the winter, or scorching hot in the summer, consider investing in double pane windows. This web page explains what double pane windows are in an easy to understand and helpful way:
I'm not sure which state you live in, so I can't give you a solid recommendation on a window installation business to hire. However, I do suggest searching for a "glass shop" on Yelp.com or Google.com, and reading through some reviews that other people have written about their experiences with local businesses.
If you happen to live in Southern California, I know the best glass shop in Orange County is Tiffany's Glass and Mirror in Buena Park. Sure, I'm a little biased because it's my dad's shop, but there are plenty of positive reviews on Yelp for the work done by Tiffany's Glass & Mirror, too.
Hope my answer helps a bit, and best of luck to you! :)