I have found that the only way to get sudo permissions for my user account was to login as root, then run visudo. At the end of the /etc/sudoers file that is now being edited add the following:username ALL=(ALL) ALL where the spaces are actually tab characters. However from CentOS 7 onwards, this has not been a problem.
While building a LAMP setup I discovered that the phpMyAdmin is not available from the CentOS repositories. So you need to use EPEL - FedoraProject, the Extra Packages for Enterprise Linux. With CentOS, this is easy just run yum install epel-release to get the repository added and then yum install phpMyAdmin will just work.
Recently whilst working with CentOS 7 and a compact install I had trouble finding the GUI for Yum. Eventually I cracked it! You need to load the "Application Installer" from Applications -> System Tools, which does look like an App Store. Just search for "Software" and install it, then go Applications -> System Tools and pick "Software" and from there you can install packages! You just need to search for them. Easy when you know how!
I have successfully used the Fedora Package for UltraEdit on CentOS and not found any issues. See UltraEdit Hints and Tips for details.