Correct bugs, Maintenance stream is (Aircraft Maintenance Engineer),
Overhaul is (Aircraft Mechanic) and you don't want to go there.
To become Licenced engineer in the future it is much easier through the AME stream, QF try's to close doors for AM's from getting ahead.
And yes the future is Avionics if you can get head around it!
Check out the Emirates Web site about what they have to offer. For a 18 year old, it will be an experience, they will look after you financially, but they will give you a run for money and be prepared for major culture shock.