I have used sabayon for a couple years, was the first distro that found and used all my hardware.
Seems to be a bit addicting as I have tried others since, sabayon is my main distro.
Is easy to update, in a root terminal, equo update then equo install entropy equo conf update then equo upgrade
Do this as you see fit and will be up to date, no need to install again. Once you are updated, you can use equo search <package name> to find what you want, equo install <package name> to install. Entropy is a great package manager.
You can find help here, The irc freenode #sabayon is great source for help, and of course the wiki is good place to start.
Once again, welcome to sabayon and enjoy