It depends where the exhaust leak is. If it's where there's a gasket the exhaust will need to be seperated and a new gasket put in. There are set labor times for replacing gaskets. Labor times are diffrent depending difficulty and location. Autozone also dosn't diagnose cars. All they do is pull codes from cars and tell you what the code is and recomemnd replacing parts. Not to say the exhaust is not causing the code. If you can provide the code maybe everyone can help point you in the right direction. Having it diagnosed by a shop may be your best option to verify the cause.