No, not really, it depends on what difficulty your playing on.
Chat with our AI personalities
Not really. If you don't die too much it will be a short campaign.
Saddly you can't. The creators of cod5 waw(which does have co-op campaign) and cod6 mw2 are different.
No, but there are individual co-op missions.
Which level? And how do I know if you are referring to Campaign or Spec Ops?
You unlock the museum, an extra level displaying all of the levels off the campaign.