New Nagios installation

I recently installed a new Nagios and now i would really like to start configurating it. I have a few questions:

  • Right now we have Cacti and Munin also: i have heard you can bind them to Nagios using plugins. How does this work?

  • What is best: Nagios or Nagios/Centreon ?

  • I have old configuration files of a Nagios v1.3. Is there an easy way out to re-use pieces of configuration in the new server 3.0 ?