How hard is it to replace the Header GAskets on my 2002 V6 because it sound like it has a loud Exhaust Leak. I have taken it to Muffler Shops and they tell me that there is no leak but still I hear a loud Leak at start up and while it is cold. Another thing is the Passenger side Cat is Removed and it only has the Driver side.... Any Ideas or how to on how to take of the Headers?