I'm a firm believer in if it ain't broken don't fix it. Been so long I've forgotten but I think 12 to 15000 rounds is the recommended recoil spring replacement schedule but I don't even adhere to that.
Unless one breaks the recoil spring is about the only one that will ever need replaced and if your having cycling issues that's the place to start. Your slide failing to lock open could be an out of adjustment slide lock spring, or loose screw on same.
The guide rod is your personal choice. The factory plastic will run till the cows come home. That being said I did put a stainless guide rod in my K40.
If you desire to swap the striker spring you can order the 5# replacement for a slightly lighter trigger pull, it's still completely safe and reliable, travel stays the same and frankly most folks don't notice the difference in pull but it depends a lot on where your trigger pull is now. Mine was on the light end of the 6# scale so when new the 5# didn't make a ton of difference, it did like any spring break in and got a little better.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."