Actually, on the back corners of my arcade, I had a little damage similar to what you described. Mine wasnt that bad, so I just took the vinyl right to the edge and called it a day. If yours is a little worse off, you can always go to Home Depot or Lowes and get a tub of wood spackle. Its really cheap and works for filling in holes and notches in wood. Just fill in the missing chunks with the spackle, take a putty knife to it, let sit, then sand and smooth. If its a really big piece thats missing, near or right on the edge, I'd say go ahead and cut out the area around it and replace it with a new piece of MDF.