You can just cut down a full size recoil spring and I recommend a heavier spring (18-20) for full house 40 loads.
There are companies that make a stainless guide rod for the 40P and this is the only CZ firearm that I recommend the stainless for function. This is because it has the recoil buffer that prevents the slide from impacting the frame during recoil. Make sure you have the buffer installed! I don't think the SP-01 guide rod will fit in a 40P.
The lower frame is a P01/P06 (compact frame) and will take all upgrade parts listed for a decocker frame:
https://cajungunworks.com/product/75215-production-legal-pro-package-decocker/The upper is a mid length slide that was left over from the joint venture with Colt and it will take the standard SRS-1 kit extended firing pin and reduced power firing pin plunger spring
The hammer is a standard decocker hammer (P01, SP01 Tactical, 75BD, etc...)
The short reset kit is an option but really should be paired with the type 2 disconnector for a better trigger feel
While your in there you should replace trigger pin with the floating CGW pin
Oh and you'll need the slave pin to reassemble the decocker sear cage
...
You should ask yourself what part of the pistol you don't like before starting down the upgrade path. What are your intentions for the pistol? It's a slippery slope and before you know it you will have to upgrade all your CZ pistols. Once you feel how well you can make a CZ trigger work with some polishing and parts you might need it.
Cheers,
Toby