I didnt replace the foam cushion in mine, but I pulled the covers off and put the seat heaters in. the covers are held on by plactic channels that interlock, not very hard to take off, a little more trouble to get back on. No special tools required. I didnt look to see how the cushions were attached to the frame. If I had to guess i would say they are glued to the frame. Order the cushions, pull the seat out, strip the covers, and see. it cant be to hard to replace. IMO.
2005 Chevrolet 2500HD Extended cab D/A 4X4
lbz mouthpiece, towing mirrors, heated cloth seats,
Airlift 5000 bags w/ onboard compressor, B&W Hitch w/ Fifth Wheel companion