I just saw your other post.
I would highly recommend taking a backup of your production server before you attempt a change, MCPC+ will download it own dependencies, there shouldn't be any issues upgrading however, just a simple case of downloading the MCPC.jar, renaming it to your current jar, replace it and start the server.
Personally I would delete bukkit.yml and let MCPC+ generate a new one (if Bukkitforge creates a bukkit.yml that is)