You're looking to change the password complexity setting you found in the "Default Domain Policy", not the local group policy. Then do a "gpupdate" and you'll see the change take effect.
Open Group Policy Management Console (Start / Run / GPMC.MSC), open the Domain, and right-click and Edit the "Default Domain Policy". Then dig into the "Computer Configuration", "Windows Settings", "Security Settings", "Account Policies", and modify the password complexity requirements setting.
Editing the "Default Domain Policy" is definitely a quick-and-dirty thing to do. The better thing to do, once you get a better handle on group policy management, would be to return the default back to default settings and make a new GPO overriding the default with the settings you want. To get you by fast, though, editing the default isn't going to hurt you.