The short answer is basically yes, and I'd suggest playing around with
the service via the web app before diving into the API.
Info on setting up and using merge tags can be found here:
http://eepurl.com/fPl3
http://eepurl.com/fPlS
You can update your list however often you want - you'll probably want
to use listBatchSubscribe for daily updates
http://www.mailchimp.com/api/1.2/listbatchsubscribe.func.php
The important thing to realize there is that we don't pull anything
from you - it is up to you to push data up to us that needs to be used
in campaigns.
jesse