... I'm worried my library and pictures and entire phone content that I've been building for four years is going to disappear!
Have you not created and maintained a Backup of all your precious Photos... Music... etc.
I When I try to go on iTunes it says it needs to be reinstalled,
Nothing should be lost... However it is Both Prudent and Recommended to have a Backup.
My phone was last backed up about two weeks ago on my iTunes, but I can't back it up again if I can't access iTunes which is why I don't want to delete and reinstall in case it wipes my library and then I won't have my backup or my stuff!
It was as easy as uninstalling and then simply logging back in and everything being as it was, as if it never needed to be reinstalled then this wouldn't be a worry or a problem:(