Excellent, glad you got it working.
And no you dont need antivirus for Ubuntu. Ubuntu is 100% immune to windows viruses and even if you somehow download an infected file or something in virtualbox it will be isolated from windows.
As for the disappearing menus sadly there is not much I can do for you there, there was supposed to be a feature to turn the global menus in Ubuntu off but it never came to fruit before 12.04.
Luckily if you hold down the left alt key the menu will return as will hovering over the top panel.
Just remember you have to HOLD down the left alt key and not just press it as if you do the Ubuntu HUD will appear.
The HUD in Ubuntu is an alternate menu system that you type in a command (say activate preferences in Firefox).
Other things to note in Ubuntu:
The side bar in Ubuntu is called the Launcher, it is very similar to the Superbar in windows 7 where applications are represented by clickable icons, there is no traditional taskbar in Ubuntus interface called Unity.
To switch tasks in ubuntu if you have multiple windows open is to hit alt+tab and this will open a window selection tool.
The most important button is the one with the Ubuntu logo in it, this is called the Dash.
The Dash is Unity's answer to more traditional menus for both good and bad.
The dash has an array of icons at the bottom, first is the home icon, then there is the applications icon.
There is a whole slew of these icons so play around, we refer to these as "lenses"
If you want more direct access you can just right click the dash icon and many categories will come up.
Each section of the dash is searchable via the keyboard so if you know the name of the application you want to use (say calulator) just type in "calc" and the dash will find it.
Getting used to the dash is odd at first for a long time windows user but once you get the hang of it it will become easier.
Another thing to take note of is the Ubuntu software center that is represented by an icon that looks like this:
Link Removed
Its the primary tool to install applications in Ubuntu, unlike windows where you install software via going to download.com or something and clicking on a .exe Software center offers a apple software style UI to install software.
Seems like Microsoft will do something similar with Windows 8
Another thing to note is that you cant move the close/maximize/minimize to their familiar places on your applications.
They are locked to the left side of the screen sadly but over time you will get used to it.
as for the video cam light issue you have, I have no idea. Might be something to do with virtualbox but I am unsure.