I unwittingly updated to 6.2 in the process of trying to secure the signal on my just-activated DSL. Now I am completely unable to do that. Nothing I've tried works. I thought I read in another thread that 6.2 (or the 7.6.3 firmware update) bricks 1st-gen Extremes, which I have. So sick of Apple right now.
Apple made available Airport Utility 5.6, but it does not install on my 10.7.5 without jumping through hoops. Once installed you should probably have access to what you need. Download the Airport Utility 5.6 from Apple, then use a software program called 'Pacifist' to open that package to get out the app, and put it in your Applications folder, inside a folder you create called Airport Utility 5.6. Good instructions are here: