very easy indeed. Replacing the bearings and whatnot requires special tools but sealed bearings last a long time anyways. Servicing the main component (star ratchey system) is really easy.
First, with the cassette still on pull with significant force and the endcap of the driveside hub will pop right off. It takes a fair amount of force though. Or the method i prefer is find an old quick release and make a slight bend at the end, now with the cassette off slide the QR skewer down the hollow axle, make it so it catches the endcap and tap with a small hammer.
When that cap is off the freehub body will slide right off almost effortlessly.
3 parts will come out besides the actual body;
2 star ratchets
You will see how the system works, quite well engineered in my opinion.
Remove the star ratchey, both are the smae so dont worry about mixing them up.
Dont spray with any solvent because you are close to the bearings, but wipe off all visible grease and apply new grease.
Wipe off all grease from the star ratchets and apply new grease.
Insert back, the star ratcheyt is secured similar to how an ISIS tool is, just the way you found it.
The whole job took all of 15 minutes