It needs to be cleaned and re-packed with grease, so drop it in a plastic cup with some solvent in it. I use paint thinner from the hardware store, and a L. A. Rams beer cup. Once the rotor is off, you'll want to pull that inner bearing, and the seal. From the outside face, a longer drift or punch will push on the cone of the bearing. This drives the cone out the back, pushing the seal out ahead of it.
Seal goes to the tray, bearing goes in the solvent.
Keep the bearings separate so you can mate the same cup in with the same cone on assembly. Get as much grease out of the rotor as you can. You'll put new grease in there after the rotor is machined. A little of that solvent and a rag will do wonders. By now, you have the makings of a brake job lying on the floor.