Legally, you do need something -that- idiot proof.
I have no doubt you are smart enough.
Someday your wife or son or daughter might have to run it. Are they all above average mechanically?
Someday you will sell your place. With the next owner be above average?
Electrical stuff lasts longer than us, gets passed on to others.
And as we look around, there are a -lot- of idiots out there. Just takes your breath away sometimes seeing the depth of idiocy doesn't it? :)
The transfer box isn't for you.
You buy it for the lineman working on the lines, you buy it to keep your insurance rates down, you buy it so any idiot can keep the power running on your place.