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First take your guitar to a luthier and see if it is worth putting time and money into. After 40 years it may or may not be worth it. Martin still makes silk and steel strings.
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True all around... 70s Yamahas were pretty good quality (for an import), I bet if it was stored properly it'll be fairly easy to put back in order.
I don't know about the DFW area, but I bet you can find a good luthier pretty quickly in a metro that size. Ask around at guitar shops other than the big chains for recommendations. Sometimes, good luthiers even work through the chains... For instance, a really good one works though the Sam Ash near me... No where near DFW though.