Until now I do all my work myself. (polishing, trigger work, exchanging or installing parts, springs, fine tuning, etc.) I dont know if you could call it gunsmithing
What I did was buy me a rather cheap CZ75. There is hardly any difference between a 75 and a S2, even a lot of parts are interchangable.
I learned a lot, made some mistakes and corrected them.
It was very satisfying to see that with my S2 I was able to work on it without asking myself the question if it shoot after I was done.
I got to add that I dont have the luxury to send a gun to GCW or CZ custom and gunsmithts are far between in the Netherlands.