I'd like to learn more about that myself. I had a trigger spring break on my Bersa once. After looking in the frame, I quickly decided to let a gunsmith fix it.
Speaking of useful gunsmith skills for SHTF, this is something else that recommends the Glock pistol. It's an entirely modular design. As long as you keep some spare parts, you can replace anything on the gun yourself with a single punch tool, and most of the spare parts are interchangeable across models. I have a spare everything for a Glock pistol in my bag of tricks.