It is not normal to replace the entire engine for a leaking cylinder head gasket. Head gaskets are normally replaced. That's a common repair on any car brand.
Catalytic converters are replaced when they lose their efficiency or when they become plugged. Without knowing what happened or why, it's hard to how your mechanic came to the conclusion it has to be replaced. If it's plugged due to being overheated from too much raw fuel going into the exhaust, it will severely limit the engine's performance and can cause engine overheating. If something catastrophic happened to the engine besides the head gasket, he could be worried there's chunks of metal in the converter that are blocking it.
Thursday, July 25th, 2013 AT 9:33 PM