Updates are free providing it's the same version of Nero i.e. you update Nero6 versions with the latest updates.
You can't update free of charge from Nero5 or 5.5 to Nero6 or Nero6 to Nero7.
Nero6, which IIRC OEM Suite 1 is one of its versions, can be updated on the Nero website to the latest version (184.108.40.206a).
However, you just might have to download and install one of the intermediate versions to be able to install the latest version.
Easiest way is via: