I also own a 2000 Taurus, with the 3.0L Duratec engine. The transaxle on Tauruses, like most FWD cars, is its weak link. If you haven't been following Ford's recommended maintenance program of dropping and cleaning the pan, changing the filter, and refilling with Mercon V ATF every 30,000 miles, you should. I follow that program, except I only use full-synthetic ATF (e.g. Amsoil Universal Synthetic ATF or Mobil 1 Synthetic Multi-Vehicle ATF). Regular Mercon V is a partial synthetic and not nearly tough enough for me. Shifting, performance, and gas mileage are so much better with full-synthetic ATF, that you will never use anything else. The difference is particularly evident when you drop the pan and observe how clean it is. Transmissions run, on average, 50 degrees cooler with synthetics, which is huge and makes a cosmic difference in everything.
In your situation, the fluid may be boiling out. Hopefully, a little preventive maintenance will save your transmission. Installing a rebuilt runs around $2,600.
Here are a couple of links that might help:
https://www.askmehelpdesk.com/cars-t...ml#post1362128
https://www.askmehelpdesk.com/cars-t...tml#post552241