You should not need to mount a CD/DVD or flash drive as they usually appear under the /media directory. You can test it with no CD/DVD or flash attached, navigate to the /media directory and insert a CD/DVD/flash and note the change. It will usually show as a long combination of letters/numbers. If you don't see anything there, post back with what you do see.
I'm surprised you don't get a GUI on boot. Can you post the name of the iso file you downloaded and used to install Ubuntu?
Do you not get any sound at all? If you have a System Settings icon on the left open it. If you don't see it, click on the Dash (Ubuntu icon in the extreme upoer left of the Desktop and when it opens just type System Settings. There should be an icon in the window labelled 'sound' so click it and you should have a number of options available to configure. I would start with the 'Hardware' tab.
Most Linux distributions use a file /etc/innitab in which you can set the system to boot to Gui or not but Ubuntu doesn't use that file.
Ubuntu doesn't, see the link below: