Advice needed: DC, static routing and DG

Hello,
I am migrating from Windows 2003 DC to Windows 2008 DC. Our previous DC was configurated by a consultat before my arrive. He configured, in Win 2003, this static routing:

Destination: 0.0.0.0
Network: 0.0.0.0
Default Gateway: 192.168.1.254 (the ip address of firewall, previously Zyxel, now Astaro :))

Each client used Win2003 IP address for Default Gateway and DNS server.

Considering that now I have to reconfigure my entire network, I'd like a suggestion from Astaro community. Which would be the best configuration? It's better to continue to use Win2008 for both DG and DNS?

Thanks in advance
eclipse79