My question is why fix something that is not broke? Clean the M38 Turk Mauser rifle and leave it in the wood. I'd be more concerned about headspace and if the bolt does not match as well as the bore condition. Some rifles are best left not taken out of the wood. ID each firearm, check for matching bolt and bore condition, then all matching, and write information on a tag. Clean the bolt & bore and oil. The old owner most likely had a record book with serial number, ID, and facts such as all matching, if rare, ammo type, bore condition, if refinished, and price paid and where it was purchased. Most save bill of sale. Maybe even an old C&R book?
Clean the bores and bolts, leave wood as is. Most do not want buggered up screws or refinished or waxed wood. Most buyers want a clean bore to see what they are getting. If it's me , I want a matching bolt and an intact non refinished or over cleaned stock. Get the correct sling and bayonets for the firearm. Best to ID and leave as found if selling. That is my 2 cents of info.