I just finished installing an Apex sear in my Shield .40 with no issues. It literally took me like 10 minutes from start to finish. I didn't purchase the whole trigger kit, because I didn't want to deal with removing the rear sight. I was really only interested in lowering the trigger pull.
I now have a nice 4.5 pound trigger pull. If you leave the stock springs in place you will get a 4.5 pound trigger. If you use the springs that come with the kit it will give you a 5.5 pound trigger. Again, I only bought the Apex sear, and not the whole kit. I'm very happy with the results. Thanks Apex!!! I will be going to the range on Monday to see how the new trigger improves my accuracy.
If I can do this anyone can, lol!!! It's a good feeling to learn a little about the gun that may save your life one day. I don't post very often, but the people on this forum are simply outstanding. I read the forum everyday. Thanks guys!!

Steve