My Husqvarna MZ54 lawn mower hit 100 hours and needed the first hydro oil change. The service manual for the ZT2800/3100/3400 is available online. These are also used on Bad Boy Mowers and probably many more.

The tool and material list I used is here:

3/8 Socket and ratchet
11/16 Open End Wrench
5 quarts 20W50
2 HydroGear filters Part Number 52114
Drain Pan and oil funnel

Please don't forget to purge the air out by pulling the bypass valve open and rocking the control arms forward and backward.