I Honestly couldn't tell you norm, can't say i've ever had to swap an axle that way. My advise in removing the rears is to find a large 3 jaw gear puller, and remove the tyre so you have a clean pull at it, bit of heat from ideally an oxy/acetelyene set, then it should just pop off. As to welding it I would recommend taking it to an engineering/machining shop. I think i would be looking to have a new shaft turned up and swap the sprocket over. but you are probably still looking at $200+ to have this done.
