Are your running AC when this happens....if so it may be the case that holds the heater core. This happened on my 98...they changed the design of the case in 99 or 00...a bulletin, not a recall...typical ford.
If you remove the center console you can reach your hand up under the pass side dash and feel the leak where the case clamshell is...a crappy design
If your car is under warranty then you are fine. Mine was not so it ran about 850 or so. The part is cheap...125 or something. The labor is a killer...they have to remove the dash, etc. Im fairly inclined...brakes, h20 pump, but I would not attempt this...to many ways to F-Up the electrical system, airbags, etc.
Good luck...Seriously