What could cause my car to blow a head gasket ?

What is your question?

My car has 50000 miles and has been serviced every 3000 miles. Got service engine soon light and noticed the temperature was all the way up. Pulled over and had it towed back to town. Took it to Nissan dealer and they said the head gasket had blown and that the aluminum heads were probably warped cause the temp got up to 286 degrees. I had purchased an extended warranty when I bought the car and they sent a inspector to look at it and he wants engine torn down, dealer says it needs a engine. Don't know what to do ??