I changed mine. Just beat the old bearings out with a socket appropriately sized and a hammer. Then beat the new ones in with a socket too....just go easy on the start so you have it lined up good.
I got bearings from ESM, but he doesn't supply people. I later tried rounding up some of my own bearings and didn't come up with much. Seems like the INA part number doesn't match to anything. But, if you take the bearing somewhere I am confident you can get replacements. You may have to buy in bulk though. I found one place that could get them for $3/each, but needed an order of 100 or more.
And I don't know anyone who has successfully removed the rotors from the gears and reinstalled them. I know a couple who have tried and not had a fun time with it. Better to leave that part alone. Everything else breaks down though.
Micah