only way to service it is to drop the tranny unfortunately. yes it can be regreased. if it s a sealed bearing, you can pop off the dust seal and repack it wit h grease..... Use Redline cv-2 grease.... it's really great stuff
with bearings, it s a bad idea to cheap out... I know autozone does stock some good brands and it sounds like you didn t go for a good brand or it s just bad luck
I would only buy bearings made by F.A.G, Timken, Koyo or SKF
when you drop the trans, might as well slap in a new Pilot Bearing too......... one makes noise when the clutch is engaged, the other when the clutch is not engaged.... I can never remember which does what and it s a great idea to replace both anyway when doing a clutch
good luck