For the cosmo on the stock, try putting it in a black plastic bag (Contractor bag) on a bed of newspapers. Seal it up, and place it on the dash of your car/truck in the sun, windows closed...
Is your concern about the bore related to value, or shooting?
I can't comment on value- as I own a couple of 91/30's (one action used for a LR custom rifle) and shoot them.
If you're going to shoot it, you should slug the bore to determine your bore/groove diameters.
http://7.62x54r.net/
http://www.gunandgame.com/forums/mosin-nagant/