Here's what they did: Light sanding (just by hand-no power sander) and then a gel stain over the old stain. (This is why I tore out that missing piece of wood, to take to the paint store along with a piece of my new flooring. They played around with the stain color until they had a perfect match.) Then a few coats of spray on polyurethane. It is a project a DIYer could definitely take on.