Don't know whether this has been asked yet, but are there ranked matches for the 360 version? Didn't see an option for it.
Also, for that one shot one kill part, I was able to reach extraction point by hiding inside the ticket booth near the bumpers. :lol I hide inside, towards the back left and just waited till the extraction team showed up. I kept getting spammed with nades, but the booth is indestructible and if any strays get inside, its easy to just throw them out. I didn't beat it yet because I got my sniper confused with the extraction point and loss my sense of direction. But if you're looking for another way through the level, this is one.