dhcp on linksys wrt54gs

I've had the wrt54gs for a while, its working great without dhcp.
when I turn on dhcp, all the information returned is correct except for
the gateway ...it reports itself as the gateway, but i have nothing
hooked into the wan/internet side, as i'm wanting running a straight
router-style setup.

I have it set to router mode with all my pcs hooked into the
LAN/wireless side (including my bsd gateway) and my topology looks like
this:
pcs -> linksys > freebsd(gateway) -> internet

also, i have tried setting to gw mode and putting the bsd box's cable
into the wan/internet side. that was also a no-go.

Is there a way to get this router (using dhcp of course)to use another
box for the gw?

Maybe i'm wrong, but with the original firmware you could`t do that.
it's posible that you need to use other firmware see
http://www.wrt54g.com. on those firmware are RIP support, OSPF, BGP
Routing, etc. check the link.