Are you connecting the pc to the router, or the DSL connection first? At work here, the Lucent router handled all that for me. AMERIVOICE1 (or proxy, exchange and firewall) just needed to jack into the thing. Inside the router, the port and IP forwards were setup. Really nothing special.
The reason I ask is the part about the lan. Now, if this is going to act like a proxy, then 2 NICs can be used nd the DSL one can be delayed from loading up till after the boot process (for the different adapter module). The second NIC can then be connected to the LAN thru your hub/switch.