Pictures updated frequently, so check back.
Your blower wheel provides air into your home. It must be cleaned to keep airflow at a maximum rate.
 Dirty blower motor will cause premature failure. 
Although the heat exchanger is cracked, it wasn't large enough to cause the CO detector to alarm, but this will cause headaches and could cause sickness! Have your system checked!  
Make sure the company you use to install your equipment has the knowledge about the duct system as well. (no hanger)