don't worry, it's easy (promise)
Messages on the iPhone are stored in a sqllite file inside of the backup. If you have no idea what a sqllite file is, well, then you have a little more homework to do, namely install sqllite so you can... read a sqllite file. :)
Once you have that installed, you need to grab the file within the latest subdirectory you can find inside the directory Library/Application\ Support/MobileSync/Backup/ called 3d0d7e5fb2ce288813306e4d4636395e047a3d28. This file has your texts in it. I suggest you copy it somewhere else in case you corrupt it by mistake using sqllite. Once you have it, just run sqllite [your backup filename] to load the data.
getting the data
The following query will retrieve the texts stored in this file, in a nice pipe-delimited format:
If there's more data you're looking for, this will tell you the columns in the table (sqllite doesn't use desc or describe):
The output you get should be usable in Excel or any other number of tools if you want a different backup of your texts.
