Jason, the seatback and sides interlock together along the seams. After you remove the screws at the bottom, wiggle the panel about, it will be soon clear how the panel joins with the sides of the seat, its kinda like a zipper without the teeth.
I did this repair just two weeks ago, I found the gadget that runs the headrest up and down the seat has broken into pieces, its just made of hard nylon. There is a little gear in it that is turned by a little shaft running from the motor, which is tucked down low near the seat pivot. It's a cheap part (the hearest gear part), if you open up the back and look in, it will be apparent what is wrong.
1995 MB E320 Wagon
2001 BMW 530i
2007 MINI Cooper S (!)