Well, it is difficult to restore just one section of the stock. I have try to do this and it just does not match up.. you have to strip the whole rifle and restain the entire thing. You can get a good stain stripper at Home Depot, get some steel wool, lots of sand paper in different grips and a nice space heater to let it dry. I recommend TWP water proof stain, clear then go over it with the type of color stain that you want. This will take some time and the checking is very difficult to do. So if you are pretty good with wood, go for it, if not, save yourself the time and $ and get another stock from a gunsmith or online at stockysstocks.com If its a fairly common factory rifle, there are plenty of options.
Good luck!