2000 Nissan Xterra exhaust system problems

I have driven my 2000 nissan xterra for almost 2 years now with normal driving, no off road driving or abuse of my vehicle. Recently I discovered that after a few weeks of an overwhelming smell of exhaust in my passenger cabin that the exhaust manifold is in fact cracked. Now on many occasions I have a very young child in my vehicle so I've had to leave him outside till the exhaust smell has dissipated and I can only assume it's no longer making it's way into the cabin.

My 2000 nissan xterra with less than 51,000 miles developed a crack in the passenger side exhaust manifold. I have maintained this vehicle at a very high level and even though it is designed to be driven off road my vehicle's off road experience is the occasional gravel road. The vehicle is not driven "hard" or beyond normal driving conditions. The cracked developed without any indication other than a strange "hissing" sound from the engine and a slight exhaust odor inside the vehicle.