Don't hold me to this but you should follow these steps first. LINK
After following these steps your phone should be just the way it was before (photos where they should be, etc).
Then you should just download the jb software and jb it and you should be good to go. After jb'ing you won't have to do anything but start looking for apps and tweaks to start personalizing your phone how you want it.
There have been cases I believe in backing up and restoring where contacts haven't been added and whatnot but I personally haven't had anything like that happen. I also have not had experience with an app like you have so I don't know how that app will handle pics and vids when it comes to backing up and restoring before you jb.