We did so on our 01 Contessa before we sold it and looking at our 00 Marquis, it looks like the same set-up. The headboard is held to the wall with screws. The screw heads are covered with plastic caps, usually the same color as the upholstery or wood. The caps will pop off if you use a knife or thin blade screwdriver to pry they off. Remove the screws and the headboard should be free. You will probably need to pull the mattress away from the headboard to get at all the screws. Reupholstering it is pretty straight forward. All you need is a glue gun and stapler. Be prepared to spend a lot of time removing the original staples, I found a screwdriver with a small blade worked best. For re-stapling, use an electric or pneumatic gun (latter is preferred).
When reinstalling it, tighten the screws but not so tight that the plastic washer gets distorted as then the caps won't snap into place.
Good Luck,
Steve
