Definitely what I was going to say. Now, if you have all html files maybe it will be harder and you'll have to get fancier. I'm sure a program out there might be able to do it though.
If you hve individual files, use dreamweaver, repace all body and html bottom tags with your script..
If you are using wordpress, there is a plugin for google analytics: Go to wordpress.org and search for Google Analytics for WordPress
i think that you dont need to add Google Analytic Code in Every Page, just Go through Footer file and Add your code thats shit. You entire webpages will be tracked by Google Analytics.