This is going to be our new task…here are some of the tips for how to start this

Within the first Active Directory site or sites you are upgrading, the first Exchange 2010 server role you should install is the Client Access server role. When you are ready to begin your deployment, it is recommended to upgrade a single Active Directory site at a time to Exchange 2010. Depending on the size of your Active Directory site, this might be a single Client Access server computer or a load balanced array of Exchange 2010 Client Access servers. The recommended order to install the Exchange 2010 server roles is the following:

1. Client Access Server role
2. Hub Transport Server role
3. Mailbox Server role
4. Unified Messaging (UM) Server role
5. Edge Transport Server role

When upgrading to Exchange 2010, you can’t perform an in-place server upgrade on an existing Exchange server

More article on this please click here

 Microsoft Exchange Analyzer, click here