1. that error message means you are trying to run 2 apt-gets at the same time. Make sure synaptic is closed before running apt-get on the command line, make sure you are not running updates at the same time etc.
2. You may have to configure sudo, you can use su in the command line to achieve a root shell
enter password, prompt should change from $ to #
then enter commands, but be careful as all commands are now ran as root and you can screw things up.
Type exit at the prompt when done being root. Prompt will change from # back to $
3. Depending on which desktop environment you are using you should have a gui to help you configure your internet