Can you give ma a list of parts that you would need to replace like gaskets for the plenums and others to be able to get your spark plugs changed for your 2002 Mistubishi Montero?

You would need the CORRECT plenum gasket (they are supposed to be reusable but why take the chance?), a NEW set of engine specific plug wires, and a set of engine specific sparking plugs. Note that "engine specific" is stressed due to the fact that there were two different possible engines fitted to that series vehicle.

Please be sure to check your smog hoses for hardness/brittleness as some have to come off and you may want to have replacements onhand before you disable the vehicle. Good luck.