Read this .....
You will end up with two Apple ID's. Use your new Apple ID for the iCloud services
and for your me.com email and use your existing Apple ID for iTunes. You must
use your old Apple ID in iTunes to play any past and future iTunes store purchases
Read this Apple support document about using different Apple ID's ...
Also before switching Apple ID's backup each Calendar as a seperate file and
backup your Address book. You will need to import them into your new iCloud