I haven't taken a close look at the seats. I work for the company that makes the seats for the Avalanche. There are probably four nuts holding the seat onto the track assembly. You could remove those nuts, leaving the track attached to the floorboard. This will give you access to the seat trim, which most likely is attached to the cushion pan with plastic j-clips. There will also likely be velcro holding the center seat panel seams to the foam.