depends on what they were showing, changing springs is not a problem for most people with mechanical skills but the issue comes in to working the sears that is where most guys get in trouble. I've seen hammers, triggers and other sear parts on various guns destroyed by guys that didn't completely understand the way the parts work together. Doing one right can be time consuming, it's not uncommon for me to take a gun apart two or three times before I'm happy with where the action is. It's very easy to go too far when removing metal.

I won't be wronged. I won't be insulted. I won't be laid a-hand on. I don't do these things to other people, and I require the same from them. John Wayne-The Shootist