Can breathing in gasoline fumes get you sick?

Yes. Volatile fumes from gasoline, glue, paint, etc..., are bad because they diffuse throughout the body after inhalation. The fumes one smells at a gas station are diluted by the air, so don't cause illness. If one purposely sniffs gasoline or glue, or accidentally gets too much fumes while painting inside a closet, he can get damage to the lungs, brain, etc..., especially with repeated exposures.
Sometimes. With most chemical fumes/smoke the amount of harm depends on the length of exposure, how much and whether or not you were in a well ventilated space (or wearing protective equipment. Ask your question again with a bit more details about your exposure.