PIX 520 - In over my head

We are moving an existing 4 server setup from a datacenter that supplied a firewall solution, to a home/office that does not have one. We obtained a pix 520 we are trying to implement but are completely lost.

Our network is an online interactive game site that utilizes 4 servers.

SQL/web server (win 2003)
2 game servers (win xp pro)
mail server (win 2003)

Each server can currently be accessed via RDC with an external IP. TPC/IP settings show an internal IP on all servers. The 2 game servers are accessed by the SQL server but never directly from the end user (except by RDC by administrator). Servers are connected via a Cisco 2900 series switch.

Our new setup has a block of 13 IP's. Our connection comes through a 4 port SMC router supplied by Charter. We do not have access to the router admin but have confirmed with Charter that DHCP is off.

Our pix 520
firewall version 6.3(3)
PDM 3.0(4)
768 ram, 1397 mhz, 16 mb flash
it lists ethernets 0-5

There are 6 card slots. From left to right the first two slots do not have any exposed connections. Slot 3 has a single port card (rj-45). Slot 4 has a 4-port card. Slot 5 has a fiber port. Slot 6 no exposed connection.

I can connect to the pix 520 and the 2924 switch via hyper-terminal. This is where I am over my head. I am not sure how to setup and structure the firewall. I need step by step instructions from this point. I understand how to assign IP's, netmasks, etc. I am just fuzzy on WHAT to assign.