Front-End mail server help

I have a w2k domain in mixed mode with a exchange 5.5 server. I am about to integrate the exchange 5.5 into AD. After that i will install a e2k mail server into the organization "which will be a backend mail server" and move all my mailboxes from the 5.5 to the 2000. I will than pull the exchange 5.5 server off the network. I than want to implement another exchange 2000 enterprise server as a front end server into my DMZ for Outlook web access. I am looking for specific information on implementing the frontend server from installation to configuration especially in relation to how i am getting the traffic to go back and forth since the server in my DMZ will have an external IP. I assume i will have to modify my router to translate the external IP to an internal one our set it to pass traffic to the internal exchange server. Thanks