Backing up iPhone to new macbook

Hi guys! This question has been answered a billion times, but mine is a little different.

My PC died (oh bummer! 😉) so i went out and bought a new macbook pro 13"!
I'm pretty familiar with itunes BUT I dont have a backup saved from the PC.. My iphone 5 is synced to my old PC obviously.
I chose the option 'Back up to this computer' on my new macbook and it did a backup, but i'm not sure what it actually did.

I am wondering what it actually backed up and if i was to sync some music, what would I lose?
I'm not worried about losing my current music, or photos. But I cant lose my messages, or notes.

Other than that everything can be deleted!

Help?