Ability of Starfleet/Imperial vessels to conduct operations

[Mr. Oragahn]

That is stuff I know but I didn't see the relevance.
The fact that he's been on it for years would actually prove that he's been literally self trained on it early. The fact that years were necessary, when he had free time outside of his slavery duties, highlights that assembling parts which were not meant to be assembled wouldn't be that easy, especially if Anakin needed many pieces. We can't know what delayed the final assembly.

The point being that the work he had to do couldn't be utterly complex either. Anakin never had to cobble the pieces of the fusion reactor together.
He's talented about this, but his bio and background explain this.
It took him years, but it's not like he had free time everyday. We may, above all, have an issue regarding what genius means, implying that he had a natural super ability for mechanics.

[Praeothmin]

According to Wikipedia:

A genius is a person of great intelligence, who shows an exceptional natural capacity of intellect, especially as shown in creative and original work.

Notice the creative part.
True, we do not know if Anakin had to adapt different components for them to work toghether, or if he only chose components made to go toghether.
But we also do not know that he didn't need to adapt mechanical parts or components.

So it could go one way or the other.

In either case, he's a gifted individual that develloped his gift probably witht the help of Watto, seeing as how his mother seems to possess no technical skills, and it would be for Watto's great advantage to have a slave have such talent at tinkering and at repairing mechanical parts and components...