Here's a link to the Wolff site. Springs for SMITH & WESSON NUMBERED SERIES Semi-Auto Pistols
Here's a pic of the Sear Spring. No need to change it unless it's bent way out of spec. When I disassemble my Gen 3 pistols I don't even remove it.
The most common spring to replace is the Main Spring to improve double action pull, Hammer Spring on the Wolff site. Easy to change, just remove the grips.
You can also lighten the double action pull by putting in a lighter Draw Bar Plunger Spring, Wolff calls it the Trigger Return Spring. Trouble is you have to take the pistol apart.
Here's what it looks like from the top of the frame, pistol assembled.
And how you'd see it disassembled.
I would try the lighter Hammer Spring first. Get several weights and make sure that you don't go so light that you get light primer strikes and a useless pistol.
While you're at it, get several weight Return Springs. Even if you don't use them, they don't cost much and it will save you shipping if you want them later.