The turbine housing? Some cracks are normal and happen after only a few miles. MAke sure its bad before you replace, and you wont find a used housing with out cracks.
The vfaq, for porting the turbine housing I believe, shows pics of some normal cracks. As long as they arent so big that you can see right through them, and they dont hold the WG open, there wont be a problem. I would bolt on the turbo if it looks ok, if you dont get excessive lag then the housing is fine.