Kristin, John and others that have issues with Exmerge:
This is unfortunately something that might but also might not work for you depending on when your appointments were created... we had some customers that used this option with success. We do not have a newer version of Exmerge, no.
Now for the good news: the updated version of the Outlook tool that was mentioned as option #1 in the post above is scheduled to be released next week, should be early in the week. This is the tool that will have additional options that will help with rebasing the resource mailboxes. While realizing it is getting awfully close - I would suggest you wait until the tool is out, as it should help especially if you have a lot of resource mailboxes.