Sigma triggers are a little funky. You will want a good gunsmith to look at it. I believe that S&W will do the job themselves if asked. Someone posted something to that effect here a while back. Check out some of the older Sigma posts. I'm sure it's in there somewhere along with another guy that sent his to a guy that he named in their post.
If you want to take a little off the trigger you can replace the striker spring and that will lighten it up some. Wolfe Spring sells sets of three for like $8.00 last I had looked. It's pretty easy to do and inexpensive. I did it to my 40VE and it did work well. I later did do a little stone work in the trigger later but really time will take care of that for you if you wait it out. Some will say you get light strikes with a lighter (striker) spring but I used a reduced spring in mine. I actually took a few more coils off the spring too while I was at it. I don't advise people doing that though. It's really not needed. The reduced spring will work well enough on it's own.I fired a ton of reloaded and factory ammo through that weapon before I sold it off trying to get to fewer pistols of the same caliber. A friend has my old one and uses it every week and it's still going great.
Anything other than that it pays to take it to a qualified gunsmith. Even doing that spring can get a little tricky. You have to be able to remove the plastic plate off the back of the slide. And remember. There's a striker under that cover with a spring. It will fly out if you're not careful.