Unusual problem(?) with iTunes and my iPhone 4S

[PapaNoHair]

I just purchased an iPhone 4S thru Sprint and I am in the process of setting it up. A few years ago I had a .mac address and that is listed as my ID on iTunes. I could not get that address back so I set up a new address at me.com. I got it set up thru iCloud ok but I need to add extra memory before I can upgrade to Lion on my iMac. What happens to my music when I complete the above process and begin the process of syncing between my iMac, iPhone and iCloud. Is there a way to either 1) change that .mac ID to the current me.com ID, or 2) will the music automatically transfer to the iCloud and iPhone if the ID's are different? Thanks in advance for help!