Sorry, but if you built a report based on a connection to say an ODBC driver, then the report is really bound to the set up. It is a pain to change, as you have found out.
How my company gets around this issue is that our application pushes the data to the report, so all it cares about is the schema of the data....where is came from is of no concern.
There is a program that will update CR files in many ways, but I can't remember it's name