But if I use yum can I still install the webmin rpm and the webmin turtle firewall sepeartely or before I start yum? Without a graphical interface to tell me what packages are included in yum I have ...

maybe try yum check-update first, to ensure you have the latest package data. otherwise disable fastestmirror. set "enabled=0" in /etc/yum/pluginconf.d/fastestmirror ...