Wow, if you have the SBG6580-2, its time to upgrade. Thats a pretty old device that didn’t even have simultaneous dual band broadcast. It was user switchable between 2.4ghz and 5ghz. But not both. 

Even cheap dual band routers these days are simultaneous. Plus it doesn’t support very fast speeds being a 8x4 modem. 

Might be worth checking into something with a little more capability. 

Not sure in terms of your label but if you hardwire a pc/laptop into it, you should be able to access it and change the ssid/password to whatever you’d like. 

Wi-Fi Security Key is your Wi-Fi password.  If you’re referring to the password to log in to the settings, the default is either password or motorola.  If the login password is changed, you’ll have to hard reset by pressing the reset button for 15 seconds and log in with password.