You said it's gooey, not crusty, right? If it were crusty, I'd say mebbe ear mites but not with gooey ears.
Gooey dark discharge is most likely either allergies or infection. You can try a little benedryl (I use children's chewables for Pip when his allergies are acting up). If benedryl is not available, than any children's antihistamine that does NOT contain acetaminophen. Try it for a couple days see if it helps or not. If it does, great...if not, then you'll have to steal yourself up for a vet visit. Can you put your dog in a carrier for the trip? It's even safer than seat belts.

When cleaning ears, use Witch Hazel instead of alcohol. It has both antiseptic and anti-fungal properties and is much more soothing and less irritating than alcohol. Clean the ears every other day. If you plan on taking the dog to a vet, then don't clean the ears for a few days because the vet is going to want to look at the type of discharge.

Also, take a close look at your dog's diet. No corn, no wheat, no soy. If the ear problems become chronic, then take the dog off of all grains and sugar (meaning, no beets or squash, yams or dog treats that have been sweetened)) Add some salmon oil or flaxseed oil to food. Also, at 17 you should probably also be adding a supplement with digestive enzymes just to help your dog utilize all the nutrition from their food.
Good luck, and please keep us updated.