[mindslight]

There is overlap for design/analysis. The problem is that overlap is insufficient to do mains wiring safely. Engineers doing their own work is an inspector cliche for a reason.

> Using a wire nut properly is a bit tricky but not the worst thing in the world, and I don't trust a rushed contractor to tighten a wire nut any better than myself.

This ties right into my point though. Low power circuits generally don't use wire nuts, and even when they might, they don't use thicker solid wires generally used for mains wiring. So you most likely learned wire nuts as their own separate skill, rather than from low voltage circuit work. My point is you've got to learn all those mains details in their own right, rather than thinking it's just like low voltage/power wiring.

(I totally agree about trusting yourself versus a rushed contractor! Emphatically yes - please do learn to DIY! My point is about the learning path to get there)