I do it all myself.
I'm a former semi-pro motorcycle mechanic (worked in a local independent HD shop). I have plenty of training. And plenty of tools, although not every specialized tool needed for bicycle work.
So working on mechanical stuff comes naturally to me. And, like a poster above, my wife expects me fix everything, including her car.
I know my limits and am happy to pay a pro when I'm outside my comfort zone. I don't mess with plumbing or electrical stuff. But so far so good with bicycles.