If you install the Apex kit keep your factory springs, it's easy to change them back. What will void your warranty and can't be easily changed back is polishing the internals. I would gladly give up my warranty for the improvement I've made to my trigger, what I don't like is S&W won't sell parts to fix it if something happens. I might trade up to a Glock at some point and will have a hard time buying anything S&W ever again.

BTW If you make ANY changes TEST TEST TEST!!!! If you might need the gun to save your tail you want to know it's going to fire. For testing I like to use CCI ammo as they have hard primers. Steel case ammo has even harder primers, but I just don't use it.