You dont need to uninstall Fedora.
But i suggest doing a backup of your data nontheless.
Windows 8 will probably either just overwrite the MBR (or EFI, whatsoever), but it might erease your Linux installation just as well.
If lucky, all you need to do after the Upgrade from Win7 to Win8 is to boot off a linux live media, chroot in it and reinstall grub into mbr.
That could look like: http://sea.hostingsociety.com/?p=Art...ons.html#error
NO garantuee included.
Hope this helps.