Question Regarding Steam?

Hey guys I'm new to Steam and wanted to join the GTA4 GWJ game that was running today, but I couldn't figure it out, I haven't done any kind of multiplayer gaming in a few years and all this new fangled technology has me confused. First off how do I get in to the GWJ games? do I just look through the games for one with a GWJ tag? is there a private server? also what voice chat should I be using? I've heard Ventrilo mentioned but as I said I have no Idea, any help would be appreciated.

Might want to ask on the PC GTA4 thread too.