I did this just 3 months ago:
http://ftp.support.veritas.com/pub/support/products/NetBackup_Server/264250.pdf
- I changed the old server to a media server
- On the new server I imported all the tapes I needed to import (page 247)
- Then, I did a copy of all the images on the imported tapes (page 239)
- And finally, I expired the old images, so the new images becomes the primary copy. (page 246)
Jordi