A vehicle in a dream usually represents our physical body. Do you feel your body wouldn't make it up the steep hill? I don't know the symbolism of there being no parking at the top. When you walked back down the wheels had been changed to old ones, I guess rendering the car un-driveable. You may be receiving a warning about the state of your physical health. Maybe it's time to do something for your health that you've been putting off? ie. diet, exercise. What do you think?