Final drive leak Hitachi ex60ug

Hi all I guess this question has been asked before but the final drive on my little Hitachi is leaking hydraulic fluid and I just had a question
Is it only gear oil that the cone seals keep in or does hydraulic oil also rely on the duo seals
Or is it possible to just remove the motor and service the seals whilst leaving the gearbox in place
I removed my opposite side and found the duo seals were ok just needed to do the motor seals
It's way quicker to remove the motor and do a seal replacement
Any thoughts greatly appreciated in advance regards Tommy in Australia

What usually happens is the seal on the motor output shaft fails and then hydraulic oil is pumped into the hub gearbox which then gets over pressurised and then the duo cone seal leaks. Some motors can be removed without touching the hub except the sun gear should be removed as part of the process. Seal failure is usually due to worn bearings so they should be looked at as well at this time.
If you are doing this job yourself it's crucial the hydraulic motor is full of oil before starting the machine at the finish or you could be up for a new motor.
BTW welcome to HEF. Where on the big brown land do you hail from?