From Suse's web site:
To start the upgrade you boot from the DVD and start installation, at some point you will be prompted to either do a New Installation or Upgrade, at that point you select Upgrade and continue with the setup.
So "upgrade" should be a built-in option.
And yes - make sure you a) have a good backup, and b) have plenty of spare disk space before you start :-)
'Hope that helps .. PSM