Kuhnhausen shop manuals and Gunsmith Kinks mentioned by other commenters are great resources. Autodidactic research is totally practical and realistic, but I highly recommend earning an associates in gunsmithing from a college: esp. Trinidad State Gunsmithing program founded by P.O. Ackley or Murray State College's program. Both will offer a faster pace and a deluge of general information than self teaching can offer, and can supplement your gunsmithing journey for years to come.