Really, a good trigger job can be done by a competent person, slowly, patiently, with the PROPER TOOLS. These tools can be acquired from Brownells (i.e. the SW rebound spring tool if working on a SW). The benefit of doing our own job is that we can spend hours upon hours doing a job that a gunsmith must do in about 1 hour to be able to make money on his work.
Now, a good gunsmith can do in an hour what takes me a couple of days, but I'd put my last few trigger jobs (SW V Comp 627, Encore and old style contender) against the best I've seen from the big guys, especially that V Comp. The combined cost of the jobs, parts, tools, etc, was about $50.
The downside of doing your own work is that, if you screw it up, you just bought yourself a pack of trouble, and danger, that'll cost you at least a bill, maybe two, to fix.
So, the moral of the story is that if you know that you know that you are patient, competent, have the tools and the time, go for it. If you are not 100% confident that you have all of these traits and assets, there is no shame in taking your arms to a good smithy, handing him $60 or so bucks, and getting a nice piece back a little while later.
FWIW, IMHO.