Yes , well fortunately I have made a recent time machine which is a week old before the iTunes 12 update. What you would have to do is back up anything on a separate external drive or partition between the time you made the big time machine update, to this present day. Any songs you added to your library that you did not buy through iTunes such as your own music you made, or from CDs you ripped. Anything else as well such as documents, artwork etc... back up stuff you recently done from the major time machine update to present day.
Then reboot , press the alt key, then choose the system restore icon, and apply a system restore from time machine backup , this would erase everything on your drive and restore it completely to the time and date of the time machine backup.
You cant copy library listing direct because iTunes 12 changes the library format from version 11 or 10.(only music files you can, but would need to re-import them)
Then when its complete , place your files, you backed up on a separate drive, before the restore. If you bought stuff through the iTunes store, in the time from the time machine set date to present, you can just re-download them again, because they would be assigned to your apple ID.. (problem if your ISP does not give you unlimited broadband).
Thats what I did, and since I have a relatively new Macbook Pro, it came with Mavericks installed on it. I am keeping it that way for many reasons such as disliking flat design, and their has been drama with CS6 apps, wacom drivers, memory issues with some apps etc...