Since the original file is a no-go...
I have a suggestion. Don't use your home scanner. Head over to print shop or a fed ex store or ups store or whatever and see if they have a scanner capable of scanning the image with as little loss as possible.
An at home scanner, no matter how good, is going to have some pixel loss. While that wouldn't be an issue for a digital cover, it could be an issue for a print cover (you won't know for sure and a lot depends on the image until you get a proof). The best scan you can possible get will hopefully eliminate most of those problems. Also, let them know that the purpose of the scan is for print, not digital (will make a difference).
While it's definitely feasible, expect the worst possible result and be pleasantly surprised when it works
