Hunted caribou in Iliamna area of Alaska at -35 F. My 7mm Mag didn't freeze, but my dad's mdl 70 375H&H did. He wiped the oil off as well as he could, and it worked fine. His bullets dropped like a son of a gun though. Perhaps there are more loose tolerances in a Mauser.
I had my bolt body replaced for 75$ in parts and same for labor. Mine was a sporterized mauser with magnum-length action. Chances are a gunsmith will have some used parts, else the smith or an online search can return list of suppliers of commercial spare parts.
There is a guy on here WildinAlaska that does gunsmithing.
When all is said and done, there is a lot more said than done.