I have seen much worse than that repaired. Find yourself an old body shop that has been in business for 30 years or more. Ask around your town if anyone still does lead seam repairs. If the guy can do lead, he will have the knowledge to fix your roof for certain. I don't mean the repairs have to be done with lead, just that someone that has been around that long knows how to work old metal. Good news is that it is a lot more workable than the thin stuff used the last several decades.