You need to put a micrometer on the pin and measure it in several places, as they wear with flat spots and eccentrically. The darken area is wear (lack of grease) often the needles wear more then the pin, looking at the movement and the pin I'd say the bearing is shot. Quick way and only as a guide is clean out the bearing with brake cleaner, once all the old grease is out shake the bearing if it rattles it's shot.
Check the seals, if they're hard/brittle replace them or your new bearing will fail in short order.