Vets do clean out dog's ears. The dogs don't like it much though. Unlike people who just get a waxy build up that needs syringing, if a dog gets cruddy ears, there is usually a reason...mites, an infection, sometimes an allergy. Yes, best thing is to pop the dog to the vet and get the vet to take a look. sometimes they can tell just by looking at (and smelling yucko) the wax, sometimes they need to look at it under a microscope.
A word of warning. There are powders you can get to treat dogs' ears yourself, the most common is called Thornit. Its fine to use it in tiny amounts on a cleaned ear but if you put it in on top of crud, then it mixes with the crud and the whole thing sets even harder. its called concretion. The reason that I know so much about this is because one of mine has got a pork allergy. It manifests in the dirtiest filthiest ears that you can imagine. It took about 8 months to get it diagnosed and sorted and for much of that time, I was deep cleaning and medicating his ears 4 to 8 times a day. The vet was brilliant and I did a ton of research on the net. I know know more about dogs' ears that I ever wanted too and some of the photos and videos are too gross for words!