make sure that the ticket agent knows. as long as you're flying on american eagle (the parent company of american eagle is AMR which also owns american airlines) you will be fine since they codeshare with NW airlines. but just double check with the agent that takes your bags and you'll be good to go. also double check your baggage claim ticket. as if it's not checked to your final destination you could have problems with it being unloaded in Chicago
Time Wise-your good on the way back, but it might be tight on the way there, depending the the size of the airport and the location of the gate.
your luggage will transfer over to the next flight, even though it is on a different airline, just make sure you tell this to the worker at the check in counter so they know to check it on both flights.
Have a good trip!