PLEASE HELP - EURGENT

PLEASE HELP!

I recently got a new iphone 5s for my birthday, I created a new appleID and made numerous purchases. Unfortunately my phone is cracked and it is going to be repaired, the most likely case is that they might be able to replace the screen. If not they might replace my phone. One of the requirements before I get it serviced is that it must be backed up and have the latest software. I've updated it to IOS 8.4 I believe. I don't usually use this method of storing data. For my other devices I've used icloud. I would like to know whether if I potentially do go a new phone will I be able to "pick and choose" what photos, music etc what I would like onto my new phone from my computer. Or do I have to transfer everything from my computer to my new phone ( which I would hate to happen ) !!!

My phone gets serviced on Wednesday so I would really appreciate and help.