Since it hasn't been pointed out at this time, I'll tell you that it's not at all difficult to do your own action job. All you need is a selection of rebound and main springs, the special tool for installing the spring in the rebound slide, some stones, and the S&W revolver shop manual. All of which are available from Brownells. BTW, make sure to get that tool for the rebound spring, I cannot concieve of any way to install the rebound spring without that tool.
Read the manual at least twice before starting and the most difficult task will be to get the sideplate started back into it's nest, which takes a bit of experimentation the first time you do it because it requires learning the "feel" of how to do it smoothly. It probably took me 30 to 40 minutes to get the sideplate back on my model 67 the first time, now I can nest one in in under a minute.
BTW, the newer MIM guns incorporate features that used to have to be added during an action job, so basically there is nothing more required than replacing the rebound spring and perhaps smoothing the DA sear on the trigger. However, if the gun has seen 500 or more DA trigger strokes the DA sear won't need any smoothing at all, they seem to be self polishing. I also found no need to smooth the surface of the rebound slide since it was quite smooth as it came from the factory.
BTW, the rebound spring can have a big effect on the SA trigger pull in addition to the DA pull weight. I have a 12 lbs. rebound spring installed in my 617 and it breaks at a bit under 2 lbs., which is light enough that it requires complete attention to the trigger finger at all times when it's cocked. I also found that while the 12 lbs. spring functions perfectly in my 617, that same spring will have issues with the trigger reset in my 10mm 610. I would recomend a 14 lbs. rebound spring for the first choice, it will produce about a 3 lbs. break on the SA sear, works well in double action without any reset issues, and reduces the DA pull to about 8 1/2 lbs.
There are also reduced power mainsprings available. However, the selection is somewhat limited and most of the lighter mainsprings come with the notice that they will only function properly with Federal primers. Another option for reducing the mainspring power is by backing out the strain screw. However, doing this can also cause issues with weak primer strikes and failures to fire. In addition, any strain screw that isn't fully seated will tend to back itself out over time. Because I am not a fan of making adjustments that cannot be undone, I am not a proponent of filing the strain screw. I prefer to fabricate shim washers to fit under the head of the strain screw from standard shim stock. With a small sheet of 0.005 inch shim stock, and an investment of some time, it's a simple matter to make up a batch of shims that will allow the strain screw to be backed out in 0.005 inch increments while maintaining a fully seated strain screw. This allows tweaking the strain screw in staged increments so that you can find a postion that permits the lightest DA pull while maintaining reliable ignition with most commercial primers.
Now, one final note. As previously mentioned, installing a lighter rebound spring will reduce the SA trigger pull my a noticable ammount. It you decide to install a lighter mainspring, or reduce the tension on the standard mainspring, you'll have to experiment a bit with the rebound spring weight in order to get a SA trigger pull that is a weight at which you are comfortable with. I suspect that with a reduced power mainspring and a light rebound spring that it's possible to get the SA pull down to the range of 1 lbs. or possibly less. I would not consider that to be safe even if it doesn't show any pushoff. So part of doing an action tuning for the lightest reliable DA pull weight will require experimenting with the balance between the rebound spring and the mainspring tension. So, if you want to do your own action tuning, get a selection set of the rebound springs. I'll also tell you that the K, L, N, and X frame are very easy to work on and one advantage to doing the work yourself is that you can undo anything that produces an issue you don't like, such as a super light SA pull or dependence on one particular brand of primers.