I bought the trigger, DCAEK for my full size 9&45 (even bought a barrel for my 9) but left my Shield 9mm alone. It was pretty good from the factory.
I'm not sure about springs alone though, the sear and plunger made a huge difference in my full size guns and I wound up using one stock spring to keep the pull from being too light. I guess some have had luck polishing the internals though.
Just be sure you actually have a bad trigger first. Sometimes we change things just to be changing things.
Initial Shield triggers were awful. I looked at some a few months ago and they were much better
