re: How much space you need (in terms of GB) - where are the songs now? Can you check and see how much space they take up now? That would be the most accurate way to tell - because they might need more or less space depending on how compressed they are, how long they are, etc.

For example, on my computer (Windows 7 PC) I can right click a folder, select "Properties" and it will show "Size". One of my music folders (I have music in different folders, based on type of music) is 4.82 GB for example. I'm not sure how many songs are in there, as it's further divided into a bunch of folders.

Hope that helps some... I'm not sure about the Android stuff.