Updating things like KDE or Gnome can be a pain, I wish you luck
As for readline, you should be able to run "rpm -e readline" (just like that, which will erase the rpm.. although you may have dependencies) and then run "rpm -Uvh readline.rpm" (which will install version 5, I suppose)
A *very* dirty method is running rpm --nodeps <whatever commands you want to give it>. rpm --nodeps will install/uninstall a package without worrying if shit depends on it.