I have a 617 that I've done a bit of tuning on and it can help with the DA and SA trigger pulls.

For the single action pull, you can stone the SA sear angle on the trigger to get a lighter weight. However, I do not advise doing this, especially for a first time endevor. One issue with stoning the angle on the sear is that you are basically shaping it so that it assists in letoff, which in my opinion will increase the wear to the sear notch on the hammer. Over time that will lead to pushoff and require replacing the hammer. A much easier and reversable option is to install a lighter rebound spring. Installing a 14 lbs. rebound spring will lighten the SA trigger pull to about 3 lbs. A 12 lbs. rebound spring will take it down to about 2 lbs., however that light a rebound spring will require a full action tuning or "lazy" trigger return will result and may cause the lockwork to lock up until the trigger is manually pushed fully forward. Personally, I recomend the 14 lbs. spring, it's been fully reliable for return in my guns and I feel a 3 lbs. SA trigger is near perfect.

You can also do a bit of work with the DA trigger pull and feel. However, in a 22 rimfire there is a real limit to how light you can go with the DA trigger pull or misfires will result. On my 617, the DA triggers measures at 9 lbs. 2 ounces and it has proven perfectly reliable with Federal bulk and Winchester Xpert HV. As for how I tuned the trigger to this weight, it's pretty simple, I made a 0.010 shim that fits under the head of the strain screw for the mainspring. Bascially, I just reduced the length of the strain screw in a manner that I could reverse.

Now for some tips.

One is to save your fired casings, you can use them to dry fire the gun if you place an undimpled area under the firing pin.

Two is that you'll want to purchase a trigger pull gage, it will save lots of trips to the range to check for reliable ignition and it will also save you from having the purchase a new strain screw if you cut yours too short. I happen to use a Lyman digital, at only 60 dollars it's a real time saver on getting an accurate read on the weight and worth the extra money. If your budget is really limited you can use a cheaper spring scale, however getting a reliable read with these can be a real challenge.

You'll also need a special tool to install the rebound spring in the rebound slide. I would also suggest a Gunsmiths screwdriver set, it'll greatly reduce the chance of buggering up the screws for the sideplate. Along with that, you'll want a 6 inch Arkansas stone and some honing oil. These are available at Brownell's, Numrich's, and other gun smithing suppliers.

As for parts, all you really need is a 14 lbs. rebound spring, however Brownells sells a multiple spring kit of various weights you can experiment with and the kit that has one in each weight is inexpensive.

Finally, you'll want to purchase the Smith & Wesson Manual by Jerry Kuhnhausen. This manual not only details how to fit and repair a broken gun, it also fully details the steps for an action tuning. If you follow those steps to the letter you'll find you get an excellent result.

As for a new mainspring, IMO it's not needed, reducing the mainspring tension with the strain screw achieves the same effect at zero additional cost. However, I would suggest purchasing a spare strain screw just in case you overdo it when shortening the strain screw in your gun. I would also suggest an inexpensive digital caliper so you can measure your strain screw for length as you shorten it. As for the shim I made up, that required shim stock, a 0.147 diameter drill, and a diamond burr on a Dremel to shape it to a 0.218 inch diameter after drilling the center hole.

Another note, shoot the gun for at least 500 to 1000 rounds before you do any work on it. This will not only help to pre-condition any sear surfaces it will also allow any rub marks to show on the hammer or trigger. If you find either the hammer or trigger is showing evidence of a hard rub on the frame you can purchase fitting shims for either the hammer or trigger.

Now my final note. Shipping costs add up when you place an order from mutiple sources. I've found that it's most economical to single source anything needed and order everything at the same time. Another reason for doing some shooting before going into the lockwork, paying 15 dollars in shipping for a few dollars worth of parts just isn't economical. Bascially, make sure you know every single item you'll need before placing an order.

As for cost, if you total up everything I've listed it'll probably add up to at least 200 bucks. That's a lot more that a full action tuning by a gunsmith but if you're into shooting wheelguns it will pay for itself in the long run.