It's hard to tell for sure from the picture but my guess is that all this needs is some sanding, by hand will work, followed by finish - which can be wipe on. Materials will cost very little but it will take some time. If you wanted to get fancier, you could use a stain or dye to darken the wood and reduce the sun bleaching that affects walnut. Many other things are possible, like checkering the stock, but I wouldn't. Without the checkering, I would hesitate to go to a slick finish like polyurethane - but that is purely a practical consideration. If appearance is a greater criteria than practicality and you like the look of poly, you could do that and the stock would be better protected. Wipe on poly works fine, it just takes more coats to get to an equivalent thickness of finish.
I would probably just hand sand it to 220 grit (starting at 100 unless there are deep scratches to get out) and rub some Tru-oil on it. That will darken it a little and make it look more like it did when new. The owner can easily do that themselves, it would be a good beginner project and something they can be proud of when they are done. Risk is very low as long as they are patient. Walmart sells the sandpaper and Tru-oil.