Ford: overheating in a 96 Ford Taurus, blown head gasket, head gasket leak

Question
I own a 96 Ford Taurus 3.0 I have been overheating for over a week now off and on and when I turn off my car it leaks out water and coolent out of the radiator cap. My husband changed the Thermostat today and then we went for a drive we stoped at 3 places and no problem, the gauge in the car read normaly, and when we shut off the car at the 3 rd place and it leaked out more water and coolent ( Im gussing about a gallon or so of water.) We called someone and he said to let the car cool fill it back up and leave off radiator cap and start it up to see if we see bubbles when we reve up the car, and we could have a blown head gasket. No bubbles but when we turned off the car water came pouring out of the cap. please help... do we need a new Radiator? or is it a blown head gasket?

Answer
have it pressure tested, find out if there is a system leak first. look on the front edge of the motor and as best as you can on the back along the seam between the head and the block, look for green stains or wet spots, if there are none you may still have a head gasket leak, but it is internal, smell the exhaust, if is has a sweet smell (hard to describe) it may be burning coolant, check the oil if it looks milky like chocolate milk then its internal. have the water pump checked.