Hi I just got my friend's old iPhone 3G and it has about 1000 songs on it which i want to keep.

Is there a way I can add these songs to my exsisting library of 1000 songs?
I want to jailbreak this phone but I know that I'll have to restore it and I will lose all the music on it.

So if there is a way to store all the music on my iPhone into my itunes library could someone tell me how please?