actually you CAN switch from goblin to gnomish, or vise versa.
go to tanaris and then go to steamweedle port, then go north up from the dock untill you see a house with some gnomes in it, in that house there is a book, read it and it will let you respecialize from one to the other.
go to tanaris and then go to steamweedle port, then go north up from the dock untill you see a house with some gnomes in it, in that house there is a book, read it and it will let you respecialize from one to the other.
Unfortunately, wrong. I'm L40 and 300 engineering with goblin spec. Took this bloke's advice, went to Tanaris and talked to the NPC, looked at the book, and nothing. No option to either drop goblin or change to gnomish. I wish you could, but in my experience, you can't. With every other crafting profession you can in this manner, but not with engineering specialty.