Netbackup upgrade from 8.3.0.2 to 10.1.1 - Linux Redhat

Hey everyone.  We are in the planning stages of upgrading our netbackup environment from 8.3.0.2 to 10.1.1.  Has anybody completed this upgrade before.  Our catalog is over 1TB.  Does anyone know how long the upgrade takes?  Any gotcha's?

Thank you,David