Uninstalling a package is not the same as upgrading one. When a package is uninstalled, any files it uses that are not needed by other packages on your system are removed. Changed configuration files are copied to <filename>.rpmsave so you can reuse them later.
Like verifying and querying packages, you can remove a package through the buttons on the right of the glint window or through a context sensitive menu. Remember that when you make a choice from a group's menu, the operation is performed on all of the packages in that group, so be careful!
Once you've begun the uninstall, glint asks for confirmation, showing a window like the one in figure 9.12. All of the packages that are about to be uninstalled are listed. You should look at them all to ensure you're not about to remove something you want to keep. Clicking the Yes button will start the uninstallation process. After it completes, the packages and groups that have been removed will disappear from any windows they were in.