If the stock is 80% I would agree that leaving it alone would be the best thing to do. However, if you do decide to refinish, strip the original finish with a chemical stripper. If you do decide to sand, leave the checkering alone! Sand as little and as lightly as possible, and final sand with a fine grit sandpaper.
All in all, 80% isn't too bad on a rifle of that age. I'm guessing you're going to hunt it, and if that is the case, it's probably going to get another boo boo or two anyway. I would say that if there is a chance you're going to sell it down the road, enjoy it the way that it is, and remember there is a story behind each mark on that stock.
