so painfully simple... pull the headliner board, run up to the local fabric store, lay the board on the table and the lady will cut you however much headliner material you need. stop by Home Depot, get some 3M 77 spray adhesive
rip the old material off, brush/dust the reminants of the foam material off, give the board a healthy dose of the spray adhesive, lay the material on it (start from one end and kinda 'roll' the material on so you don't get bubbles or creases)
trim the matrial to fit the board, etc.
reinstall
makes the truck look so much nicer inside and is so simple to do