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.
<name>, 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.
Well <name>, you were wise to seek my tutelage! Any schlep can become an expert at the basics of engineering - the gnomes and their irradiated home of Gnomeregan are proof of that. It takes a strong mind and a steady hand (emphasis on STEADY) though to master the discipline of Goblin Engineering.
Keep your ears perked <name>, and you might learn something.