I am sure I have ever come across a whitepaper describing what you would like to do, however I did come across this discussion in the forums:
https://www-secure.symantec.com/connect/forums/split-netbackup-master-and-media-server
With regards to the specific questions you asked:
Disk: This is will be dependent on how many clients you are going to backup, as that will determine the size of your catalog and the DSSU space you require. Also, if your company owns something like Acronis, you can always increase the disk space on the disks you originally created.
CPU: Since you can always add more CPU to a VM, you should monitor performance for your environment and add additional CPU's should 1 not be adequate.
Memory: Again, monitor memory utilization on the VM. If you find the VM is swapping excessively, then you may need to allocate more physical memory to the VM.
Regards,
Benjamin Schmaus