Ballad of gay Tony questions!?

Is ballad of gay tony worth getting? I know it's got cool stuff in it and all that. And is it an add on? Or another disk with new missions and stuff? And I play online with my friends on gta4, so if I get ballad of Fay Tony,can I still play with them if they don't have it? Like, on ranked? And if they DO get it, with me, is there a new live thing, like free mode, with the new vehicles and weapons we can use? Just cinder answer the questions and explain it a little mor if I have the idea wrong. Thanks