In addition to the other great answers, in adding a window it is important to check with the City/County and if you are in a PUD and/or have CC&R's to check if there are restrictions / guidelines, etc. Remember when you add a window it doesn't only allow in light, it allows people to look in and you to look out. Placement is very important not just for light and air.
and Jennifer, I too checked out your website, drop me an email I have some questions for you.
This is Jennifer and I'm an architect in San Jose, CA. The answers you've already received are correct. You should consult an engineer (or architect) for the construction detail and to help you get the permit for construction. It should be an easy change, overall. However, be prepared that a larger portion of the wall (larger than the size of the window) will need to be opened to get to the wood framing. Here's an engineer in Santa Clara that can help you, All Structural, 388 Martin Ave, Santa Clara, CA 95050, (408) 496-0930. You can also contact me, http://www.jkretschmer.com, and I can recommend some contractors in your area if you need one.