Help!!

Hi, i'm new here. But, my aunts 2002 Sebring does not have any heat. The box next to the intake manifold blew out. The box has 3 hoses and a bleeder valve on it, and it bolts down to the engine. What is it called and is it a dealer part? Also, where is the thermostat? Last question, how do I change the back spark plugs? Is there some kind of flexible extension I could use? I need to know ASAP. Thanks.