Changing Domain

Hi all...I need some advice. I just got my own internet domain. My internal network's domain is "home.lan" Is there a way to change my internal networks name to my internet domain name without hosing my server? I'm running server 10.3.3 behind a firewall with a comcast cable connect. I've got the internet domain pointing to my server for ftp/web/afp services and it works good. Do I even need to change the internal domain? I just feel everything should be on the same page. Thanks, Mike