As I said in a thread I started yesterday I did it myself to one of my P365s, and it was a half-hour job at most. The hardest thing is notching the frame, but as long as you have the right tools on hand it's straightforward. I used a Dremel tool and carefully cut close to the size needed, then finished it up with needle files. The other option of course is to buy a new frame with the notches already present. Installing the safety lever itself is easy, although that little spring and plunger is super-tiny and easily lost in the carpet if you fumble it.