Microsoft Exchange training for new admin

Hello. My shop, which is to be acquired, runs Lotus Notes/Domino as it's messaging platform. The acquiring company is an Exchange shop. Since I don't have an Exchange background, I am wondering if anyone has an opinion as to the best/quickest way for me to come up to speed as an Exchange admin. With Exchange 2007 being the platform in use, should I first learn Exchange 2003 or jump directly into training on Exchange 2007? I am considering some training videos from learnitfirst.com.