If you replace factory trigger spring with aftermarket spring, will the warantee still be good?

Not for any malfunction involving the aftermarket products. However, you can easily return to the factory trigger spring.
You should know that literally changing the trigger spring alone accomplishes little.
If you are referring to the APEX kit, it is not warranted by S&W, and S&W will not work on any problems related to the kit.

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Science plus Art

i wouldnt say it does little. I used the APEX spring kit, and it helped the trigger out tremendously for me. SD9VE still doesnt feel like the gun for me, but the trigger is a lot better now

I only replaced the trigger..not any springs, and that alone satisfied my quest for a suitable trigger.

The APEX kit is more than just the trigger spring, so my statement stands about just replacing the trigger return spring alone not changing the trigger pull very much.
Take the slide off and pull the trigger to see how little tension is on the trigger return spring alone.

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Science plus Art

I put the whole kit in mine, but before I did it was really knarly

Now its sweet and smooth

Put the stock parts in the new parts bag and throw them in your gun drawer.

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Smith..and Wesson..and myself.

You better stop fondling with that thing or you will go blind.

My brother in law bought a SD9VE and has put a couple of thousand rounds thru his compared to probably 600 I have shot out of mine. I put an Apex trigger in mine and thought it was so much better....which it is, but his trigger from just shooting it has gotten about the same as mine.

Speak louder...I cant see ya!!!