Is Airport Utility the only way to communicate with the Airport Extreme?
Nope, AirPorts cannot be configured through a web browser. You have to use AirPort Utility.
Windows computers can also use AirPort Utility. You just have to install it. You can use the CD that came with your AirPort, or you can download AirPort Utility from the Apple website.
As for "advanced admin settings," try Manual Setup.