Lesabre heater core ?

2005 Lesabre heater core started leaking. Does anyone know how big of a job it is to replace a heater core on this model car ?

Try this link, but you may have to register with autozone to get in, http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80cb3425