hi,had the same prob, i pulled the head linning out,binned the crappy fabric,use a leather workmans glove and the foam will 'roll' off the cardboard....easy
next get some rubber backed cheap carpet,i used some thin grey ribbed stuff leftover from a camper van job,,,,spray glue it on,then trim it around the cardboard.easy,then just refit.
before you rip off the old stuff,make a note of where they leave 'over hang'...it covers the bits the carboard doesnt,i used the old cloth as a template for the carpet