if all the fields are the same...
go to database, set database location, select the desired stored proc in the bottom window, select the 'old'/orig stored proc in the top, click update. close. Verify the database and you should be done. If there is a difference in fields that are being displayed on the report, CR will prompt with a mapping screen.
I'm not positive that will work for changing SPs, but I suspect it will. It is how I update databases when I need to change them.