1. I've never done that before, so I don't know how it would work. The only thing I know is that you need to contact someone at Zynga who is in a position to make this kind of decision, and who is also willing to discuss the idea at all. Don Mattrick is the current CEO, but I have no idea if the CEO is the person you should talk to or not.
2. Running the game yourself is not feasible unless you're already experienced enough to do so. It takes over a decade to learn how to deal with software of this complexity, and that's assuming you devote your entire life to it. It would be far easier to try to convince another established social game company to buy the game than learning how to run the game yourselves.
The most likely way that the game could stay running is if you convince Zynga themselves to keep the game running. You need to find out what they're basing their shutdown decision on, and find out what it would take to reverse that decision. It's possible that if you get enough media coverage, your protests may be able to convince Zynga to rethink their decision and come up with an alternate plan.
Re #2, As the base is so huge there are actually a number of system, network and software engineers in the YV community. Its cooperation, organization, ingenuity and funding that's required to get this going. At least one development shop seems up to the task.
I could envision other approaches that would work - including some Zynga may has not thought of.
If the base is this passionate, why not convert it to pay to play and scale resources based on demand?
Or better yet, use the YoVille Casino as a training ground and venue to promote or link to Zynga's Real Money Gaming (RMG) portals.
Another possibility would be to use the entertainment products of Zynga and GameCash as compensation (booby prizes) or as incentive Zynga's RMG Game expenditures.