Well, upon further searching, I found out that if you loosen up the cover to the seat and reach into the actual seat from underneath, there should be 2 latches. The closest one at the bottom of the headrest system locks the headrest at the upmost position. If you lift up that latch (as in pull it away from the headrest) the headrest should be easy to just push the rest of the way...
I had the same problem when try to get my seat covers on. What you have to do is lift up the head rest as far as you can then get something like a clothes hanger and stick it in that groove in the metal part under the head rest. Then you push the headrest all the way down. So then you pull it back up,take out the hanger, and it should come off.
This is for 2000 Mustang, It is easy
Every back yard mechanic has an old pair of windshield wiper blades, take the spring steal strip off one side of the old wiper blade! do not modify, It will bend and go right in with no modification.
1. push the seat cover down from the plastic grommet at the base of the post of the head rest
2, on the front , motor side of the seat, there is a groove in the headrest supporting bar.(post)
3. insert the spring steel under the grommet(below) in the slot, push down until it stops.about 3 or 4 inches.
4. gently wiggle the head rest and gently push and the spring will slip past.
5. proceed down to about 8" and you will feel resistance again, wiggle the head rest again, when you go past,
your almost done!!
6. leave the spring in place and/
7. the head rest will lift out!!
read this twice, take it off in 40 seconds, no grief.