I traded for a one of these a couple of years ago in .260 cal. While looking on the internet I saw where they have adjustable length of draw. I look on my gun and can see holes in the bottom of the stock but can't figure out how to make the adjustments. Does it require a special tool? Can someone help? Also, if I decide to sell it, what would be a good asking price? It is like brand new and been shot very little.