I'm going to take a wild guess and say that your company lacks any form of enterprise architecture plan, doesn't have strong strategic IT management, and has a cowboy culture.

You're asking the technical community how to get MAC knowledgable when you should be asking your own bosses why this is being allowed to happen at all. If the VP of Marketing unilaterally decided to move his/her department to the MAC platform, why does that person get to make or violate IT policy? If IT management sanctioned this move in advance, why are you being asked to scramble around after the fact instead of being solicited beforehand to see if you already had the requisite skill set?

Either way, you have my sympathy. This is not a good organizational situation.