Unless you need to or want to do the bearings for whatever reason (peace of mind?), all you have to do is remove the automatic hub, that looks like a plate, remove the retaining ring from the axle, take apart the top cover of the manual hubs, install the bottom part, put the retaining ring on the shaft, add grease of your choosing, align the top cover of the manual hub with the gasket or use gasket maker, bolt it together and tighten up to the specific torque and boom....that was loosely what you need to do for manual hubs, follow the instructions for more accurate details. In other words unless you need/want new bearings, there's no need to replace them.