I am not a router expert. Two of my routers run OpenWRT [they're Buffalos [1] that shipped with it], my old Linksys WRT54G [2] hangs off the Xbox360 and runs dd-wrt in its measly 8 megabytes of RAM. It and one of the Buffalos are client-bridged [3] to the second Buffalo that sits on the gateway to my ISP.

Anyway, the dd-wrt wiki is a great resource for setting up a dd-wrt or OpenWRT router or routers. Particularly the tutorials: http://www.dd-wrt.com/wiki/index.php/Tutorials

Good luck.

[1]: http://www.buffalotech.com/products/wireless

[2]: https://en.wikipedia.org/wiki/Linksys_WRT54G_series

[3]: http://www.dd-wrt.com/wiki/index.php/Client_Bridged