1 - well that just depends how many updates there are. CentOS 6 will use delta rpms where available, which greatly reduces the amount of data downloaded.
2 - the RPM you got was from repoforge, and so you can avoid downloading it, and any other repoforge dependencies it is configured to require by correctly installing repoforge as a repository for yum.
3 - Obviously you can do whatever you want, but support for newer, funkier hardware can be lacking, media applications, e.g. vlc, are not core to the main repos, wireless / hibernation etc, can suck, as that's not what servers do.
4 - http://www.linuxquestions.org/questi...pdater-884697/