As far as the trigger jobs, I can't see a new connector doing any harm. It's a very simple piece of metal. If you're super paranoid, you can stick with the stock trigger spring, but I've never heard of any breaking. Now I agree, when you start changing parts, things start breaking, but with these 2 trigger parts specifically, I don't see any issues.
I highly recommend against the $.10 trigger job. I've heard of bad things happening if you don't really know what you're doing. Granted, there are people who have successfully performed it and are happy with it. It just depends on what you're comfortable with. I trust my Glock with my life, and would never change anything that made me feel differently. A Glock factory 3.5# connector I'm comfortable with. Custom modifications to my trigger assembly I'm not. That's me.
Research, research, research.. Then decide what you want to do with the trigger.