Update: Finally found the time to deal with this ugly mess. The first step was to burn out the crud, so I ended up with four chimneys full of coals dumped on piles of unlit briquettes. Over 20 pounds of charcoal overall on all levels - the bottom (normal), and the lower and upper cooking surfaces. The thing was chock full of burning charcoal. The temp at first shot up to 500 degrees, then leveled out at 450 for well over five hours. Who knew it could get so hot? The smell was putrid.
The next day I took it apart, laid it out and liberally sprayed everything with oven cleaner. Inside and out. Lather, rinse, repeat. In the end it came out much cleaner that I thought possible. Almost brand-new. The original stainless grates still needed help, so they went though the dishwasher then a meticulous scrubbing with a scotchbrite pad, then into the dishwasher again. They came out pretty darn good.
Everything was saved. I was sure it was all dumpster bound junk when I first posted this thread. You guys convinced me to give it a try and it worked out much better than I had hoped for. The oven cleaner discolored the aluminum front opening cover, but this was the only thing damaged. I ended up paining it with flat black BBQ paint. I like the look. Thanks all for the advise and encouragement. Now to re-season this puppy and start smokin some pork...