dunno what sheldon says can't be done, but i replaced the axle and i don't know sh*t. i tapped the bearings out using only the axle (i was replacing them so i didn't worry about being gentle)

the solid axle comes with these two knobs that press on the inner race of the bearing from the inside of the hub, with the "cone" pressing on the outside of the inner race. when you get your hollow axle you need to use something like a cone or lugnut to replace these, otherwise the outside cone is going to squeeze your bearings in and eventually kill them. i used lugnuts, and determined the spacing using the original axle. its important to get this spacing as correct as possible.

getting the new (or old) bearings back on was a breeze, just use a piece of pipe and a large washer. assuming it's going in straight it should only take a few serious whacks.