Speaking as an aircraft engineer of 10 years, it is relativly easy to do electrics, replace components and even diagnose faults in the many systems on an aircraft (hyds, fuel, air, fire suppression, engines, flying controls etc etc) through years of knowledge and training..... However, when it comes to skilled skin and structural repairs, it is a completley different game, replacing parts of an aircraft that have to be fabricated in situ and to exacting tolerances takes years of practice l to get good at, it is an art not a science.

Anyone can learn a science, an Art/handskill only comes with practice...

Much like sparks and plastering if you will