LFMAO, God only knows what the hell you were thinking.
Yes, the trade requies you to visit the master engineer trainer in Gadget and give him some gold.
So you pissed off the goblins and want to make it right....
You have a few choices, First choice is to kill Bloodsale pirates, usualy thats good for some rep, if not i belive you can get the watershed bandits and the like for some rep.
If you have them REALY cheezed you will need to take a trip to Feralas, next to the dock for the Feathermoon boat you will see a lil goblin, he has some repeatable quests to help you make things right with the steamwheel cartel.