1. What do you meant "inside" why would you want to finish the inside...do you mean the little hole that holds the cleaning equiptment? If not then...I would apply a thin layer of mineral spirit to really clean the surface of any oil or contaminate. 2. Then I use boiled linsen seed oil to refinish it. I would apply light coat and let it dry to the touch then use the fine steel wool to buff the surface lightly to bring out the grains. Repeat step 2 for about 5 coats. Then I would go buy the semi-gloss finishing coating and apply two coat and let it dry. Waala you will have one fine looking set.
2. Nope just use the fine steel wool for buffing to bring out the grains.
3.Spring in the buttstock is to hold the cleaning tube thingy...becareful don't get your finger caught in there..I know many folks done that before.