they are pressed on, and thats one of the main reasons people who are handy enough to be able to fix there own sleds hate crankshafts, myself included, becase if you have a bearing issue, the only real way to deal with it is send it to a local shop that does sled cranks.
However, in your case you might be able to skirt by, but you will have to replace both bearings. If you are super super careful, you can cut the out bearing races off with a cut off wheel, get the ball bearings out, then being even MORE super super careful, cut the inner races with a cut off wheel (dont cut all the way through) put a chisel in the cut line and smack it, with a little luck you cut deep enough that the little bit of metal left will crack and you can slip the bearing race off. You do not want any cut lines in the crank or crank weights anywhere, thats why I stress super super careful.
After that if you know someone with a press, you can have new bearings pressed on. I replaced one outer bearing in my sled this year and the bearing was only $15.
