The National Rifle Association is a wonderful source of info for your gunsmithing project. They have a large assortment of pamphets and manuals specializing in your models of interest (military mauser, Lee-Enfields, etc). Try writing them for an availablity list.
Most of the larger gun shows will also have these manuals and books, as well as some of the better-known volumes by by Baker, P.O. Ackley, Carmichael, Nonte, etc.
Your local sporting goods store or large bookstore chain should have, or can order for you, the paper-back volumes of BDI (Digest Books, Inc) that are general gunsmithing references and specific sporterizing references for your mauser.
I started with M93 Spanish mausers and gravitated towards M98 mausers of every description.
Best of luck in your project, and above all, have fun!
John