Not terribly hard. If you have changed your brakes before it is just a few more steps. Been a while, but here is what I remember.
Loosen Brake Calipers
Remove Calipers, Carefully rest them where the break lines are not effected
Wash hands to remove break dust
Remove grease cap from axle, try not to bend it. Flathead used carefully will usually do it
Remove retaining pin, do not get it dirty
I think there is a washer? Might not be, can't remember, remove it
Dive into the grease and grab the old one
Run you finger around, remove as much grease as possible
Wash hands again, no pumice
Put grease in your palm and press new bearing into your palm until completely greased (Continue putting new grease into palm as needed for packing the bearings)
Place new bearing in
Put a palm of grease into area of bearing
Don't forget to wash hands again when switching from grease cap, to break caliper. Grease on breaks = not pretty
You also might just change both since you'll be doing one anyway. (Good time to change break pads too)
Hope this helps.
I really can't remember. That washer (if there is one?) might be threaded. You might need to borrow a tool, or get creative. Sorry I can't remember.
Perhaps someone else will respond too.