I have what I think is a 1983 Trek 620, which I bought from a friend about 1986. I love this bike and put on about 5,000 miles a year, mostly commuting in Chicago. This morning both seat stays cracked where they are welded to the seat tube. Is this repairable? If so, any idea where I can get it done (in or near Chicago or northern suburbs) and how much it would cost?