Xyrodon

Hey people,

I'm new to this forum and to be honest I joined this out of current paranoia for my Honda. Yesterday, I was driving and for no apparent reason the temperature needle was going to "H" pretty damn fast. I pulled over, let the car cool down and decided to drive to my dealership. As I was driving, 15 minutes later the needle goes to "H" again. I pulled over, opened the radiator cap and a bit of coolant leaked out underneath. I filled the radiator with some water and drove to the dealership.
They called me today and told me my head gasket is gone. Now here's my question. Would a Honda dealership lie to make more money? I thought it would have been the thermostat, water pump or perhaps a hole in the radiator. Then again, I really don't know much about cars.
My car is in good condition and has been very well maintained. It's a 2004 Honda Civic DX, however is does have a bit over 200,000 kilometers on it (yea kilo's, this Honda's in Ontario, Canada). I find it extremely hard to believe (forgive my ignorance) that a 2004 Honda can have a blown head gasket. What can cause the head gasket to blow?
I actually took it to the dealership in Milton, Ontario is anyone here knows where that is...

Any advice and feedback is welcome!