You might check to see if it's the bearing that's the problem before you go with a case insert.
It could be that the case is fine and the bearing isn't, but it's more than likely the case.
Either way, you'll need new bearings, so order the bearings and check before you send it off to have an insert put in.
Alternatively, find yourself a cheap set of cases for a 250...that might actually be cheaper than getting case inserts.