will change the value in a hegative way (it's not really a "collectible" gun or stock or you would not have been able to buy it as a field grade from
CMP
).
You can do anything you like from a simple Murphys Oil furniture "soap" to stripping it completely with Blue ZIp Strip (or oven cleaner) and refinishing it. Little hint, typical ugly greasy dirty CMP stocks aint collectible, unless they have a nice crisp original WW2 cartouche on em, etc. Do yourself a favor, don't worry about ANYTHING you do or don't do to that wood. Honestly, would you rather have the crappy looking "field/rack grade" wood in the first picture, or the exact same stock and handguards "cleaned" up (with oven cleaner no less) stock in the picture at bottom?
Oh, "patina" is usually a synonym for dirt and/or grease. If so, again, fa-get-about-it.
as for steaming out dents, the ONLY way to do this (where it works) will for SURE result in stripping the wood of finish anyway.