I'm also looking to get the 200,000 point co-op achievement, I haven't played this in awhile but just send me a message on Live anytime I'm usually around.
I do not accept random friend requests or party invites without having a message first! It's not to much to ask.
4 stars rating, over 180 posts since I signed up in 2009 & my stats erased, and still no email response telling me why. Very Strange.