Using a Hitachi EX200-LC2 with around 10000 hrs that I am thinking the seal on the swing motor reduction gearbox went out.  Checked the oil in it and found it low, put some gear oil in it and then ran it for a couple of hours.  Got out of the cab for a little bit and noticed a white oily fluid covering the slew ring.  I am assuming the oil drained out of gearbox and combined with water caught in the turntable.

Anyway, how hard is it ito replace the seals or does a guy need to plan on replacing the gearbox?  Or is it something else?  There is oil on the floor in the compartment that houses the swing motor & hydraulic valve stack, but it wan't obvious that a hydraulic line was leaking. 

From an operational standpoint, you couldn't tell there is anything wrong.  We are used to turning wrenches, just wondering what we might be getting into.  Thanks for any advice.

Nathan