In all fairness by the looks of the carbon buildup on the outside this skillet is due to be reseasoned. I doubt the dishwasher will do much to help; this thing needs a lye bath or electrolysis at this point.
I just stripped my 20+ year-old 10" lodge because the carbon buildup was flaking on the inside. The pan is better than new now as the rough finish has worn considerably (though it isn't glass smooth). I have a lot of fond memories of meals made in this skillet and plan on using it for the rest of my life even though I can afford and own arguably better quality cookware these days.