The short answer is no. There is no current way to manually update itunes. If the automatic update isn't working, uninstall itunes, and download the newest version off of the website.
Update the software in iTunes and it will do it for you.
New iTunes software can be installed to update the previous version. Only the iTunes software is updated the iTunes library with your music/videos etc. is not affected by the update.
iTunes 9 requires QuickTime 7.6 or later. If you are running an earlier version of QuickTime you will need to update it. The iTunes installing process should let you know if you need an update but will not do it automatically.
Plug it into your computer and iTunes will open automatically. If you don't have iTunes download it from apple.com. When iTunes opens you will see under devices your iPhone name will be there. Click that and then press check for update. If there is an update available, download it.
Sync it to iTunes.
iTunes
Only the iTunes software is updated your music library will not be touched by the update.
You have to update via iTunes on computer
iTunes should ask you if you want to install it. iTunes should not install it when syncing without your permission.
go into its tab in itunes and click update
There is no way to update your iPod from your iPod. You have to do it on iTunes on your computer.