Marcia,
I have a similar setup to Anthony's but on a D-link router where I use http://www.dyndns.org for the external web address to the dynamic IP address assigned by the cable company. If you have a static IP address on the router, it's even easier to manage.
I would also agree to turn off DMZ and work through port 80 ("Virtual server" on the D-link router) as a way to protect your system and internal network.
Cheers,
Bob