I have two linksys routers and I have one set up as a repeater-bridge and I use the firmware dd-wrt. Check it out and see if your router can use this at http://www.dd-wrt.com/site/index

After that, just follow the instructions to make your router a bridge - http://www.dd-wrt.com/wiki/index.php/Wireless_Bridge

If you want to use the default firmware on the router, then you will probably have to do more digging to see how to make your router a bridge