Latest version. Do i need to backup my data?

I see the latest version from October is still available for download.
Do I have to backup any of my folders before I download the new version?
I don't want to lose any of my stuff and settings.
If I do have to backup, which folders and files do I have to backup?

Thanks!

If by "stuff", you mean your inventory, that's all stored server side, so don't worry about it. The SL software is simply a viewer. Think of it kind of like Web browser. If you update your browser, it doesn't delete the Internet. Likewise, updating your SL viewer doesn't delete anything in SL. You could even uninstall the viewer altogether, and your stuff would all still be there.

As for your settings, there's a small chance that updating might reset your preferences. It doesn't usually, but sometimes it happens. If you really want to, you could back up your preferences data before upgrading, but I wouldn't bother. It can sometimes create more problems than it solves. Best advice, just let the installer do it's thing, and if you have to redo your preferences after, it only takes a few seconds, no big deal.