Hello,
Welcome to the world of Linux :).
First I suggest installing Beryl, however it has been discontinued do to it remerging with another organization with similar software, so I would recommend installing Compiz Fusion (beryl plus Compiz) you can get information installing it at the link below.
http://ubuntuforums.org/showthread.php?t=481314
Next after you’ve installed it you may wish to install Emerald, which was a window manager in Beryl but the new Compiz fusion doesn’t include it so we will install it so you can use the old Beryl themes.
To install emerald go to the terminal and enter this
sudo apt-get install emerald
Once both are installed we need to add them to startup. To do this go to System, then Preferences then go to Sessions. Go to startup programs and click add.
Name it Compiz you like and for command put this
compiz --replace
Then click ok, once done click add again, name it emerald then put the following in the command box.
emerald --replace
Logout then log back in, you can then change any settings from the preferances menu for both Emerald and Compiz Fusion, to install new Emerald themes go to www.gnome-look.org and download any beryl theme you like, open Emerald and click Import, choose the theme and it will install.
Justin
P.S. If you would like to install a bunch of neat Emerald themes right away open your terminal and enter the following code.
sudo apt-get install emerald-themes
Hope this helps 