2001 Chrysler Concorde Head gasket/CAM sensor

OK I was driving down the road 65mph the car started to sputter (like it was not getting enough gas) went about 2 miles and it stalled at a intersection it started and I drove it less than a mile and it stalled and wouldn't start. I let it sit till the next day and checked to see if it ran out of gas it had plenty of gas and it started right upso I headed for a mechanic when it got up to operarting temp it stalled and wouldn't start called for a tow and by the time the tow arrived it started and the driver drove it onto the truck. The mechanic ran a computer diagnostic and said it needed a crank sensor and a cam sensor. When the mechanic fixed this and did a full tune up I picked up the car and drove less then 15 miles and the car made a clanking noise and stalled at an intersection. I started it and pulled it into a parking space (less than 50 yards) shut it off because there was a rattling comming from the front top of the engine (there was no smoke or steam comming from the exhaust) I called the mechanic and he sent a tow truck. The next morning the mechanic said that I had blown a head gasket and there was coolant in the oil and I needed to replace the engine. I asked what the rattle was and he said that it was probably a a spun bearing but apparently he had not done anything past discovering coolant in the oil.
Would the computer diag shown any indication that this could have happened.
Does this sound like the engine really needs to be replaced, I thought head gaskets could be replaced
what do you think I should do?