You should really ask these questions in the rooting sub-forum as that is what it's for but...
You should back your data up regardless of whether you intend to root it or not. Once you start making changes to your phone when you don't fully appreciate all the possible consequences, this becomes even more important. Unfortunately, it's harder to back up unless you are already rooted but other people have faced this issue so a search of this forum should show you how best to backup an unrooted phone.
Something else you need to consider is that all the 4.3 stock ROMs have Knox Security built-in. This means that rooting your phone will likely as not blow the eFuse meaning you may have difficulty returning your phone under warranty and you won't be able to restore your phone to stock condition ever.
If you are prepared to put up with this, there are guides in the All Things Root sub-forum that explain how to go about rooting.
Make sure you read up about this before you jump into anything. Rooting isn't hard, but if you don't follow the instructions properly, you can mess up your phone.