I'd like to replace the sheepskin covers on the front seats of my '92 300CE. To do this, looks like I need to remove the headrest, which means you need to remove the panel on the seat back. I removed the two screws on the bottom of the seat back panel. The manual then says to lever the side panel away while pressing in on the back panel. I'm not having any success at this -- any hints or tricks? I'm using as much force as I think I should, but no luck yet....