1. What are your other components, especially motherboard. It has to be compatible and such.
2. Depending on your netbook, it might also not be possible at all, if the card you currently have is integrated and it has no extra space.
3. Graphic cards are the single most expensive components on a computer, but I cannot say a price, it depends on so many things.
4. Only in case you force it on wrong slots or use wrong drivers.
Then again you might not even have a processor and/or enough RAM.
My advice would be to simply get a desktop. Much easier and probably cheaper.