Pull back cornhusks but don't remove. Discard corn silk. Push husks back in place. In an 8- to 10-quart pan, combine Gewürztraminer and 1 gallon water. Add corn and set a plate on top of ears to keep immersed. Soak corn at least 4 hours at room temperature, or up to 1 day in the refrigerator.
In a container just wide and long enough to hold the plank (a sink, pan, or heavy plastic food bag), combine 2 parts water and 1 part Pinot Noir. Rinse plank; immerse in Pinot Noir mixture for at least 1 hour or up to 1 day.
About 30 minutes before cooking, immerse fish in the red wine mixture with the plank.
In another container, soak wood chips in 2 to 3 cups of the red wine mixture.
Prepare barbecue for indirect cooking. If using charcoal briquets, mound and ignite 60 briquets on the firegrate of a barbecue (20 to 22 in. wide) with a lid; open vents. When briquets are dotted with gray ash, in 15 to 25 minutes, push equal amounts to opposite sides of the firegrate. Add 5 more briquets to each mound of coals (10 coals).
If using a gas barbecue, it must be equipped with a control to regulate heat in the center of the grill. To heat the barbecue, cover and turn on high for about 10 minutes. Turn off heat in center of barbecue, but leave heat on opposite sides on high.
Drain wood chips. Sprinkle them onto hot coals. Or, if using a gas barbecue, put chips in a smoke box or foil pan directly on heat in a corner as barbecue heats. Lift fish and plank from liquid. Lay fish on plank, skin down, and top with 3 sprigs each of rosemary, marjoram, and thyme.
Put barbecue grill in place. Set plank and fish on grill between coals or gas heat. Cover barbecue, open vents, and cook 10 minutes. (If plank chars, squirt or mop dark areas with water.)
Drain corn and lay on grill directly over heat; cover barbecue. Turn corn as husks scorch, and cook fish until it is barely opaque but moist-looking in center of thickest part (cut to test), 15 to 20 minutes longer.
Transfer corn and plank with fish to the table. Replace scorched herbs with fresh ones and garnish fish with lemon. Cut fish in pieces and lift off with a spatula. Pull off cornhusks. Add salt, pepper, and lemon to taste.