I think perhaps the easiest method would be:
1. Make a nandroid backup of your current ROM
2. Restore your previous backup
3. Install
SMS Backup & Restore
4. Backup your messages (NOTE: There are currently NO apps that I have found that will backup MMS messages, only SMS)
5. Restore the nandroid backup of your current OS
6. Restore the backed up SMS messages
It sounds tedious but it's actually not at all. I make both an SMS backup and a nandroid at least twice a week. The great thing about SMS Backup & Restore is that it saves your messages in XML format on your SD card. If you are being harassed (as is the case with me) you can open the backup in your PC's browser and print out hard copies of everything