Help me get my dog into the pet carrier!

You could always try for a dog trainer that seems to the best option. You should start by putting treats into the carrier and see what happens. He would eventually be curious, it takes them time but you do not have a choice, especially if he is very timid and frightened. I bet he carries a lot of baggage that is why. Something must have happened; maybe that is why he is scared of big things. You should not be so worried though. Get a bigger cage for him, so he does not feel too cramped up in it. You could place a nice comfortable blanket in it, so he feels comfortable. You should leave the door open over night, keep his favorite treats lining up inside the cage and relax. Wait for him to go to it; you should not bring the carrier to him. If he is a small dog you might as well pick him up and put him into the carrier. It is always better for the animal to get used to eat so he does not feel threatened.