If you wish to learn more about Goblin Engineering, take the Manual of Engineering Disciplines to Nixx Sprocketspring in Gadgetzan.
Expert engineering yields two distinct disciplines: gnome and goblin. I only bother to mention goblin engineering because I'm a fair trainer. They like to make things that blow up, and they rarely care what is in the way - even themselves.
[player], read this manual. If you want to learn how to blow yourself up, then take it to Nixx Sprocketspring in Gadgetzan. Remember - membership is permanent and prevents joining the other discipline, so make sure this is what you want before finishing his task.