Can I use the AEBS(n) to feed another wireless signal to non-wifi devices?

Hello el rolio. Welcome to the Apple Discussions!

Can i use the new airport extreme base station to connect to the dorm network with the wifi signal, THEN feed the internet connection to my other devices thru the ethernet ports?

Unfortunately, most non-AirPort routers are not compatible with Apple's implementation of Wireless Distribution System (WDS)...so it very unlikely that your dorm's wireless router can be extended wirelessly with the AirPort Express Base Station (AX).

However, you may want to take advantage of OS X's Internet Sharing feature to share your Mac's wireless network connection thru its wired Ethernet port to the other wired devices.

Try this ...

To setup for Internet Sharing (Wireless to Wired):
Enable Software Firewall
System Preferences > Sharing > Firewall
o Click Stop to start the software firewall

Setup the Network
Wireless Internet Router > (wireless) > (AirPort Card) MacBook Pro (Ethernet port) > (Ethernet cable) > (Ethernet port) wired device

Setup Port Order
System Preferences > Network > Show > Network Port Configurations
o Verify that "AirPort" and "Built-In Ethernet" are enabled.
o Verify that "AirPort" is at the top of the list, followed by "Built-In Ethernet."
o Click "Apply Now."

Configure the Internet Connection
System Preferences > Network > Show > AirPort > TCP/IP
o Configure IPv4: Using DHCP
o Configure IPv6: Automatically or Off

Enable Internet Sharing
System Preferences > Sharing > Internet
o Share your connection from: AirPort
o To computers using: Built-In Ethernet (checked) (Note: Uncheck all other entries in the list.)
o Click Start

is there any settings i should setup on the ethernet port in network prefs?

No, nothing else should be required.