On fixing the shelf...

I have had good luck with gorilla glue. I work it in place with a toothpick, the cover the area with a couple of layers of wax paper, I then put an old Type III (junk) recoil plate in place. Then screw it down to provide the "clamping" force until it dries. Its important to make sure you do not allow glue to flow down the screw hole or you are in trouble. I use th gorilla glue because it seems to hold up once I BLOicon the stock again.

Its a cheap way to using Frank's method (I don't have all the fancy-dancy wood working tools)

Hope that helps...