They have to be either knocked out, or use a bearing puller. Either way there is risk of damage. If there is no issue, I would leave them alone. They are sealed for a reason. Supposed to be non serviceable. You may find you can't pop those covers back on after removing them.
You may be able to pop the one dust cover leaving the bearing in the wheel. Smear the grease around, since the balls rotate, grease will reach all places it needs to. Just a suggestion.
Last edited by Big B; 12-01-2012 at 11:54 AM.