You can add the chicken trinket to the list of reasons to keep Gnome engineering...it is too cool.
Gnome Engineering - WoWWiki - Your guide to the World of Warcraft
Switching Specializations
Since patch 1.10, it has been possible to switch engineering specializations. It is, however, painful. To switch from gnomish to goblin or vice versa
Press K to bring up your skills tab, click on engineering, and then click an icon that looks like a circle with a slash through it to un-learn engineering entirely.
Visit an engineering trainer and start all over again at level 1
Level your skill to 225
Visit Narain Soothfancy's house North of Steamwheedle Port in Tanaris, and read Soothsaying for Dummies.
Select a new Engineering Specialization (or your old one if you had a change of heart)
Some Notes:
You don't need to complete the quests associated with your new spec.
This system existed before LW/BS/Tailors were able to change their spec. They got the easy way of dropping their spec for a modest fee and keeping their skill level.
You will forever lose any quest patterns or specialization patterns. You'll lose Lil Smokey and Pet Bombling recipes forever, and never be able to obtain the pet recipe from your new spec.
You'll never be able to renew your membership card from your old spec or obtain a membership card for your new spec.
You may have a hard time learning quest reward recipes like Zapthrottle Mote Extractor as you'll lose them too, and have to find someone to trade you their quest reward recipe (if it's not soulbound).
Changing Engineering Specialization
