I have a number of SW revolvers (642, 686+,329) and also was unhappy with the stock trigger pull. Since I live 3500 miles from the nearest gunsmith I needed to figure out how to do the work myself. Since I do a fair bit of semiauto pistol-smithing I had most of the tools on hand. I ordered both Jerry Kuhnhausen's book "The SW Revolver, a Shop Manual" and an American Gunsmithing Institute (AGI) DVD on function, assembly and disassembly of SW revolvers (which was pretty good except Bob Dunlap, the gunsmith, is a pretty good sedative and will put you to sleep if you watch more than 20 minutes at a time). I did all three of my pistols and all function and shoot well with a smoother, lighter trigger pull.
As Jim mentioned above it is probably simpler to get a good gunsmith to do the work. He already has the knowledge and tools to do the job right.
best wishes- oldandslow