Help with saving photos/syncing music problem ?

Hi,

Basically what has happened is I synced my iPhone 5s 6 months ago to my library and all was good. My hard drive got rekt and had to purchase a new one.

As a consequence my iPhone refuses to recognise this itunes as its new home. Instead when I wish to sync with my new music library, it comes up with a message basically saying "we will erase everything on your iPhone if you wish to sync with this library". Now I would be fine with this as I already have no music on my iPhone, however I do have a lot of photos and a lot of messages which I wish to protect. I do not want them to be "erased". I know about iCloud and it currently has all my photos in their storage but I do not see why I can't just save my photos using a usb cable, iPhone and itunes.

My goal is to basically: Be able to add new music to my iPhone 5s ios 8.4, and to preserve ALL my photos and ALL my messages.

What steps must I take to achieve this?

Thanks in advance!