What should I do Windows 2003 server

Hello all,

I have a network that consists of:
6 workstations
1 Windows 2003 SB Server
1 Linksys router being used with an 8 port hub
1 Linksys WAP being used for wireless with a 4 port hub not doing anything
1 24 port SOHO hub
12 IP Addys

Here is how the network works now:
Cable Internet comes into the closet and goes into the provided Cisco Cable device(4 ports on back)
1 Port goes out to the SOHO HUB and then the HUB goes out to all the offices and workstations
1 Port goes to the WAP and not using the router ports just wireless
Each computer, including the server, is assigned a static public IP address for Internet connectivity

Here is what I want. I want to bring everything internal and only have 1 static IP. That static IP will be the router, and then I want to use DHCP on the server to give IP's. OR do I? PLease tell me the best way to secure this network!

Thanks in advance!