Why is there a gas smell under the hood of my Tacoma after having the head gasket replaced The mechanic said it was because the exhaust manifold is cracked but there is a smell of gas not exhaust?

sounds like you use a bad mechanic a good mechanic would replace a cracked exhaust manifold to start with if you can smell gas,there is obvioulsy a leak in the fuel system. this needs to be found as it is a fire hazard