ugh, sorry to hear about that.....if you do all the work yourself, it wouldn't cost much at all, but if you take it to a shop, it will probably end up costing a couple of hundred dollars at least, due to the amount of labor necessary to do the repair.
the motor needs to be dropped, the cases split, and the crank removed, to get at the bearing. the crank should also be inspected.....if it's scored too much, it'll need to be replaced.
depending on how bad it is, you might be better off getting a replacement motor.
go over to general discussion and give a holler for joey, he runs a shop and might be able to hook you up.