If you want to much of anything useful in a Greasemonkey ("User") script, you'll want to use jQuery or similar library.
Greasemonkey uses a "@require" command to pull in these libraries, but Chrome won't allow this.
To include jQuery in a Chrome user script, here's a good link which pulls in jQuery by adding a element to the page you're working on.
http://erikvold.com/blog/index.cfm/2010/6/14/using-jquery-with-a-user-sc...
