First, attempt to connect a desktop monitor to the VGA port on the netbook, just to check you are getting the whole picture on the external monitor. If you are,
It is fixable. More than likely it is the LCD screen and it can be replaced. Just google "how to replace Acer Aspire One screen" it's not that difficult if you have a precision screwdriver. ALWAYS unplug from wall and remove battery before dis-assembling.
If you are doing the work yourself, you can check that the video cable is well connected on the back of the screen - it may just be loose. Unlikely, but possible