The WEP key will be written somewhere on the Router, normally on a sticker with all the other info

And the SSID is the name of the Router, Eg BtHomeHub-67T4, it will depend on the make and you will probably be able to guess it, it will most likely have the strongest signal strange..

To Hook the PS3 up, you turn it on and go into Settings> Network settings> Internet Connection Settings and its easy from there