Sierra has that right.
Also, read all of the Admin and SFDC Install documents well before you even try to do this. The more you get right before the sync, the better off you'll be.
Do you need to add fields to SFDC to make the lead lifecycle work?
Do you understand the lead scores? Will you even do this right now?
Make sure you get your subscription mgmt or unsub lists right and migrate those over and add those fields to SFDC if they aren't already in there.