1. Copying to local disk should work just fine.
2. If you only have one server acting as master/media it should be a fairly straightforward process. The major changes were from upgrading from 5.x to 6.x. Your upgrade from 6.0 to 6.5 should be fairly simple. Check out the documents in the upgrade portal.
http://seer.entsupport.symantec.com/docs/290185.htm
3. From the main page of the upgrade portal: "For details on upgrading from NetBackup 6.0 to 6.5, see
Chapter 4: Upgrading NetBackup in the
NetBackup 6.5 Installation Guides. These documents contain the requirements, upgrade steps and other information needed for a successful upgrade. At this time there is no separate document for upgrading a NetBackup 6.0 environment to NetBackup 6.5."
That document can be linked to from the upgrade portal.
HTH Good Luck.