I did the ceiling in the cabin of my 2820 first. Previous owners had drilled holes through the ceiling to mount stuff and then removed it. The carpet was very easy to work with and extremely forgiving. Doing the ceiing gave me the confidence to do the rest.
My suspision is that a lot of the stains we Parker owners are seeing in the carpet is the glue Parker used. It's dark reddish brown, and when you pull down the old carpet, lots of dry powder from the glue comes out of the carpet. After removing the carpet, I used goof off adhesive remover to remove about 75% of the old glue. I then rolled a thin coat of polyester resin over what remained, just to seal it in. I used a 3M clear upholstery spray glue to put the new headliner back up. Its been up for 3 years and still looks great.
My suspision is that a lot of the stains we Parker owners are seeing in the carpet is the glue Parker used. It's dark reddish brown, and when you pull down the old carpet, lots of dry powder from the glue comes out of the carpet. After removing the carpet, I used goof off adhesive remover to remove about 75% of the old glue. I then rolled a thin coat of polyester resin over what remained, just to seal it in. I used a 3M clear upholstery spray glue to put the new headliner back up. Its been up for 3 years and still looks great.