Extranet architecture/setup from existing sharepoint web application

Hi,

I have two questions regarding enabling extranet

1. I have an existing web application port 80 (mymachine:80) behind LAN firewall, I want to extend it to an extranet  and make it accessible to external users who will athenticate using FBA SQL database and want them to access same content of internal users from URL(extranet.mycompany.com).

Users are not in active directory but will be stored in database. What are the steps for URL to be accessible for people outside the company (I think it is DNS or netbios but I am not very networking guy)

2. I already have a web app, tried to extend it but could not enable FBA ( it is disabled ) is there a powershell cmdlet to enable claims on existing app?