Hi Michael,
Yes, you have the right idea.
During a To Database pass you could add in a timestamp or trackingnumber. Just remember that when you do this, you will need to change the table update option to Update Entries in Table from the default of Delete table before loading so that you can update the mechanism you're using for tracking changes.
As far as measuring change, take a look at the read changed entries from AD task wizard. It will show you how to set the constants and variables you need. Just remember, if you're using V8, there are no global constants.
Matt