If you are not a rouge....
To help getyourself in alone you can use lesser invisibility potions. Alchemists at the pre-40 max of 225 skill can make them. They aren't cheap at the AH though (but not too bad)
The only problem is the only last for 15 seconds and potion cool down is 30 seconds.
When you enter the instance from the Clockwork Run side:
A) Use one potion when you enter the instance
B) Run as far as you can toward the clean room around the circle shaped upper area
C) Along the bottom of the circle are structure/pillar type object that you can jump down to where you land about 15 yards over the floor
D) Jump and land on one of those before the potion wears off
E) Wait to drink another potion and then make a dash for the clean room
Massive Gnomeregan Map:
http://www.videogamemaps.net/wow/maps/G ... Mephea.jpg