I just pulled off the wheels to replace the tires (cracked side walls),
and I'm wondering about the wheel bearings. I see a grease gun fitting
threaded into a cup, which is captured by a 'C' ring. The grease gun
fitting looks pretty rusty itself.

Should I replace the zerk and pump in new grease, or should I take the
whole cup out, flush out the old grease, put the cup back in with a new
grease gun fitting and start fresh?

Anything else I should look at while I'm in there?

Ken