I'd give them a dollar if the HG is blown.

Its a pretty hard thing to do. But I'm not saying it could never happen.

Its hard to say what exactly went down, maybe it was run low on coolant and overheated or something like that. Maybe the block heater plug rotted out and started dumping coolant out.

And it wouldnt suprise me if the Lower intake manifold is shot.

As for the 2 cylinders that are dead, have you checked the coils yet? And how do the spark plugs look, smashed/bent?