Steer and Gear wants $515 less $195 for a core. Seems to me anyone with a little mechanical ability and the ability to read the FSM could rebuild one. The only bearings you can't find are the caged ball bearings - likely not worn anyway. The bottom roller is an off the shelf item along with the seals at any bearing shop. The top gaskets are non existent but sealant works and is what Steer and Gear use.

There are many opinions on what lube to fill it with and packing it with grease is no easy task. Heating a bucket of stinking goop up on the bar-b-que also leaves much to be desired. I found "corn head grease" to be awesome stuff - but you can only buy it from a John Deere dealership. Put the stuff in a plastic bag and inject it like you're icing a cake. Its thin enough to flow into every void and fill right to the top.