Will I need new hardware to install this?

Your factory bolts work — the spacers stack between the coils and the factory perch. Verify bolt condition before install; replace any that are stripped or damaged.

Can I use this with my stock shocks?

Yes. Spacers compress the springs, not the shocks. Stock shocks will handle the 3-inch lift fine for mild use, but if you tow or carry heavy loads regularly, aftermarket shocks tuned for the lift height will ride better and last longer.

What's the best way to prep for installation?

Secure the truck on jack stands, remove the wheel, unbolt the factory coil, stack the spacer on top, and bolt it back down. A spring compressor isn't needed since you're just stacking — use a floor jack to manage suspension movement during removal and reinstall.