You probably cannot get the turbo welded and have it function properly. The machining is extremely critical on these, so I doubt it can be done. You could inquire with a turbo rebuilder in your area to be sure. If you buy a replacement turbo it will more than likely be used and without a guarantee. In that case you will need to have it rebuilt with new seals, balanced, etc. This runs about $400 in my area. Be careful of buying an Isuzu or Maserati turbo as none of the mounts will match up. For the 500 I am pretty sure that is a RHB VG1. Since they sold a lot of 500's down under, you should be able to find a rebuildable unit. They are about $100 to $200 here in the US.
End caps for the exhaust will be rare, but they exist also. I will check my stash of mufflers and see if I have any.