Some pretty good advice here
regarding markings on the wood, they are generally called cartouches- symbols or initials stamped into the wood
Some things will hurt them. Mineral spirits won't. Acetone is a thing you don't really want in contact with your skin and I wouldn;t use it on wood anyway- why bother. I've used denatured alcohol but it wasn't as effective as mineral spirits. MEK- double yikes. Keep MEK away from me- look at the MSDS sometime
If a stock is so dry that it is worrisome that the wood needs to be 'conditioned', then oiling it, to my mind, is not much of a risk at all, and after all, this type of finish was what many rifles had originally
One thing that oiling won't do is repair the wood. You'll read about how some people put stocks in the dishwasher. I caution against that. Firstly, heat and moisture are what is traditionally used to warp or bend wood on purpose. Heat and moisture can also damage cartouches. Lastly, this type of treatment can harm the natural binders in wood, and nothing under heaven can repair that. Sure, I will hear a dozen guys say "nothing bad happened to mine after I used the dishwasher!". Glad to hear it. Nothing happened to mine either- except I never ran the risk you did
Heat and moisture can, if applied carefully and locally, raise out dents that you want to remove, but just like a dent (because they really are just organized dents), it will also raise cartouches, and if you're not really careful, it can also lighten the wood locally, too. I've had great success with a hand held steam iron and a damp facecloth, but I'm very careful and I do a tiny bit at a time. It's not hard to get too aggressive.