Dealing with incapacitated pilots

What would be the proper procedure if the following were to happen:

Hijackers make their way into the cockpits and kill the pilots, at some point shortly after this, passengers force their way into the cockpit and manage to disarm and disable all the hijackers. Now with no pilots left onboard to land what happens?


Could an average Joe (just by looking at the names of the buttons) manage to contact ATC and try to get help that way.

What would happen once the ground had been notified (by radio or telephone?)

I just started thinking yesterday about what might have happened if the passengers aboard flight 93 were able to make it to the cockpits.

First thing I'd do is ask if anyone is a pilot. If yes, then problem solved.
If no, then I'd probably strap myself into that seat and contact ATC ASAP.
No doubt those many hours playing MS Flight Sim weren't for nothing.