Go to North Qeynos through the sewer and enter the instance on the NW side of the new Ironforge Exchange.
Hop on the sewer grate and then over the wall into the moat. go to the Barge and get out (bell area) avoid the guard go up the stairs and go left to the exit from the moat area. Follow the Aquaduct about half-way to the next road. The NW side if the Ironforge Exchange is to your right.
This zone is laid out the exact same as a Qeynos tradeskill instance. You need to find 3 things which can be found in different spots each time you do the quest (how much variation is unknown):
the recipe which is a flittering paper sitting on a bench (reported near workbenches and engraving tables)
used temper (to contaminate mixture) is on one of the shelves that hold the blue bottles (reported near forges)
alchemical temper (reported near chemistry tables)
There is a named mob in here who can see invis, Scribe Bogfizzle. She was one level higher solo and gave -100 Ironforge Exchange faction when killed. Also note that each of the doors is guarded by guards.
A discussion page exists which may contain more information