no just mark the cutout, drill a hole through to get teh jigsaw or sawzall blade through and go at it. make sure you wont cut into any weatherstripping or electrical.
forget the jigsaw....use a plasma cutter...i wish. anyways, when using the jigsaw just be careful not the bend the blade too much since it can break. you can mount the woofer directly to the door panel by using sheetmetal screws.