Winchester is part of the York line of equipment , you should not have a problem acquiring parts or service from your nearest York dealer.
York is a popular brand sold under many different labels.
I don't know what motor it is, if it is not the super high efficiency variable speed motor you can expect to pay approximately 150 dollars for a blower motor , that is the part. If you have it serviced it can vary widely but will probably be between 2 and 3 hundred dollars for the total repair.
If you happen to have a variable speed motor it could be a hundred dollars more. This is not likely though.