I don't think the GeekSquad guys are any better! I would say keep calm and go through stuff without getting discouraged. I know most receiver's users manual are very confusing. Most of the time the actual working of the system is simpler than the manual would indicate.
Like the previous poster indicated, no need to plug the RCA cables to stereo audio and video. Get rid of it. Let the connection be all HDMI. It looks like you have only one source which is HDMI. Is this true? You talked about cable box, so I assume it is connected to that. Then go to the menus of the cable box and make sure it has an entry for audio and that it does not have option checked for dolby down convert or anything like that. YOu want native audio from the cable box reaching the receiver.
If you have a bluray player, you will just connect its HDMI output to another HDMI input of your receiver.
If you are not getting Dolby Digital from one of your channels, try changing channels to some movie or network TV show or something to see if the receiver lights up the Dolby Digital icon. Also, if your receiver has speaker A and speaker B options, make sure only speaker A is selected. In my receiver, if I accidentally choose A and B, it only does stereo.
Good luck. I did not read the whole thread so I apologize if I repeated other people's suggestions.