While most motors can be rewound there are some motors that are sealed and therfore cannot be resealed. These motors usually need to be replaced. These type of motors are typically ones that are made to work in areas where they may be subject to water spray a good example being an AC condenser in a car.
Most of these type of motors experience carbon brush failure but looking at this post it seems that your motor's winding is short circuiting and hence blowing the fuse on the car. I would definately suggest getting this replaced though 700 does seem a bit high. Is he replacing the complete fan assembly or just the motor?