First of all,
to the Keystone Forum family. We all hope your visits here will be enjoyable, entertaining and educational.
As for a replacement awning fabric, it is very difficult to say what it would cost. There is vinyl, acrylic fabric, metal wraps all of which have different costs. Usually you can purchase the awning fabric of your choice from an RV store and install it yourself, but if you need to have someone install it for you, that would be an added expense. Often, as in the link I'm providing, you can find several different sizes available for the same price, however that's not always the case, especially when ordering from a local company.
Here is a link to at least get you started:
http://www.rvpartscenter.com/prodsel...ID=152&CID=515