I just changed the hydro oil in my Scag Liberty Z 48 last week. It has the HydroGear ZT 2800's. I found it easier to do this when the rear wheels are removed allowing better access to the filters and top port plugs, which need to be removed when re-filling the system. I used Amsoil synthetic (20W-50) which is specifically formulated for this purpose. In my case, I had to use channel lock pliers to remove the filters due to not enough room for a filter socket. From start to finish, it took about 2 hours--with at least half of that time taking to re-fill the system. If you have the room in your garage, then yes--do it there.
A completely different setup as the X-one uses a single filter at the reservoir tank, Two hydro gear pump and two wheel motors.
Per Service Manual instructions:
It is necessary to drain the system oil from the hydraulic reservoir, using the reservoir drain plug, before removing the hydraulic filter. Replace the drain plug before adding system oil.
The Hustler® X-ONE® system filter is located inside the hydraulic reservoir on the left side of the tank. Use a Hustler® approved filter element only. When changing the filter use a
5/8” socket for the Hustler® X-ONE®. The threads are right hand. This unit will take 5.75 +- qts of SAE20W50 motor oil to fill the reservior.