i agree with Yo767. All of the cabin crew that I have met have been trained to safely remove a pilot from the seat and administer CPR. I cannot believe that Mr Geek would really leave a guy having a heart attack to die rather than getting assistance from the cabin crew.
It depends.
There are degrees of severity in heart attacks. A mild attack can be as simple as a sudden chest pain. My only personal experience was with a neighbour, we were standing next to his garage chatting about car problems when he grabbed at his chest and said "I've never had a pain like that before". Within a few seconds he collapsed to the ground. Not breathing, no iris response, nothing. He was stone dead and nothing we did would have helped. We tried but it was futile.
So yes, it MIGHT be possible to help the captain out of his seat and administer CPR if his condition was recoverable but dead is dead.
I am sure that the crew would have done their best to save him if there was any hope.