If in doubt, and if no-one else responds please open a call to discuss with McAfee support.
They will be able to answer the questions.
Take a look at this thread uhaba: https://community.mcafee.com/thread/66744.
As for using your existing database, you simply point the installer to your database and provide the proper information (port, credentials, etc).
If you still have concerns, like rackroyd mentioned, a call to support would be a good next step.