[wiswind]

A good mechanic will be able to diagnose your issue.
From what you post, I would not be totally convinced that it is the head gasket, although I could be.
It sounds like you were low on coolant, but adding seemed to help.
There are several other leak points on the windstar....add a few more that are possible due to the age of the vehicle.

One common leak point, that is easy to misdiagnose as a head gasket, is the lower intake manifold gaskets.
Coolant leaking into the intake from a intake manifold gasket leak is drawn into the cylinder(s), and could lead one to think that it is a head gasket failure.
A head gasket job includes new lower intake manifold gaskets.
But if that is all that is wrong, it would be a cost savings to only do the lower intake manifold gaskets.
A mechanic can do some additional tests to determine the integrity of the head gaskets.

There is also the possiblility of a leak in a radiator hose, or heater hose.
There is also the "crossover pipe", aka bypass hose, which passes through the lower intake manifold.
This pipe also has a "U" elbow hose on the passenger side that connects the pipe to a pipe that comes from the water pump.
I show this part in one of my pictures.

So, in short, I would look for any visible signs of external coolant leakage.
Remember to look up from under the vehicle in the area of the water pump....which is mounted onto the "front cover" that is a known leak point......the gasket where the front cover meets the engine block.
Look on the ground where you park for signs of leakage.
Also inspect the radiator for signs of leakage.....particularly where the plastic side tanks meet the alluminumn fins.

There are also internal leakage points, the front cover (aka timing cover) gasket and lower intake manifold gaskets being the most common.
The replacement gaskets from FORD have been improved to address the issues that led to their failure.....so one should never have to address them again.

Take comfort in the fact that head gasket failure on a '97 3.8L is not common.