How hard is it to change front bearings on a 4x4

 

4 bolts and one heavy duty snap ring on the 4x4 shaft , not that hard it is a complete assy the bearings are not replaceable separately, you change the whole hub. The snap ring will require and very good set of snap ring pliers ,I had to go to SEARS and buy a heavy duty set, comes in pairs one small and larger ones ,the ones with the replaceable tips will break the tips

 

How do to tell if there bad.