Based on my recent experience:
(my comment to) Question one: Only if there is anything wrong with your 10d installation. In other words, if it's working (backups, restores, verify, inventory, reports, etc...) then I don't see why you would need to.
(my comment to) Question two: When I ran the 11d installer, it found that I had 10.1d installed and made some mention that it was going to perform an upgrade. The upgrade went through fine. All my backup jobs, policies, media sets, etc. were all intact and working.
Before I pushed the 11d agents out to my servers, I did a quick backup test which it complted with an exception; "The target computer is running a previous version of the Backup Exec Remote Agent. You must upgrade the Remote Agent."
But I was able to do a restore (selected a few random files from the test backup) and verify that it worked.
Then I pushed out the agent and I reran a test backup and it went through with no errors or exceptions.
Note: The above was done on my test/development network. I am in the process of upgrading my production 10.1d server and agents.
It's my hopes to have this done before the end of the year. My hold up is the following problem I've encountered as have a few other people: http://forums.symantec.com/discussions/thread.jspa?threadID=69694&tstart=0
Hope this helped.
