Yes don't forget Licensing.
To convert Netbackup Server licenses from Windows to UNIX, you need to consult with Symantec.
Netbackup server license keys are not cross platform. They are platform specific.
Generally UNIX server licenses costs more than Window server licenses.
You may need to pay more to convert your licenses over from Windows to UNIX.
If you also need to convert the catalog over from Windows to UNIX, you will also need Symantec Professional services.
If you plan to start from scratch, you will need a whole new set of licenses.
With Netbackup 6.5, the licensing scheme changed, so check with Symantec.