I have the 308 in the compact with a 20" barrel and it is a fine hunting arm. I had thought of upgrading the stock and decided against it as it would not serve any purpose for me, other than different aesthetics and I concluded that it was not worth my time or money to it. I really love the rifle and I think that you will enjoy yours as well. I am not aware of any treatment will last for a long duration to prevent rust other than frequent application of something like CLP or similar.
Please post some pics when it is finished as it may entice me to upgrade mine anyway.