2001 MPV 2.5L, 160K Shop says codes show bad mass air flow sensor and catalytic converter. I unhooked the negative battery terminal andpulled the sensor but aftermarket part would not fit. Went to dealer and told them; I got OEM part that looks like it will fit, but the check engine lightwas off and has stayed off for 2 days. Have not put in the new part. What are the chancesI fixed something? Should I return the newunused part? What about the cat; would the sensor somehow being fixed take care of that?

Also, the valve cover gaskets leak. Ihave done this onolder engines, but this looks complicated. Isthe gasket replacement difficult on this thing?