Rugs--Some stuff about wheel bearings here if you've never done it before--I tore apart both hubs and replaced bearings, races, and seals back in February or March.
Wheel Bearing Repacking Or Replacement
Also, there are great videos on YouTube.com that will show you in detail how to change lower unit oil. Probably some on there for trailer bearings too, now that I think about it. Just do a search and poke around til you find what you're looking for.