1998 Plymouth Voyager rotted pipe

Antifreeze poured out of car and car started to overheat. My husband found a rotted pipe that connects the cooling system to the rear heater core and he can get a new one at the dealer but it is impossible to get the old connected pipes off in one piece. Does he have to remove the heat shield? Can you give us any advice? Since it is so tight he is unsure how if he gets the old ones off how he would have room to get the new ones in. Any help and or diagrams would be greatly appreciated