Guilhem, you seem clear-eyed about this selection, and your surveyor should help you keep your perspective. That's hard when you have a passion for the older, simpler GBs, as I do. As well built as they were, at 30+ years of age, you're no longer just buying a boat, you're buying its story. By that I mean the legacy of care and maintenance by whoever has owned your GB during those decades when it was finding its way to you.
It sounds as though you are in touch with the seller, which allows you to look, listen and connect the dots to evaluate the boat's story. This particular GB may have a good story - I'm pulling for you and for the boat!
"Less judgment than wit is more sail than ballast. Yet it must be confessed that wit give an edge to sense, and recommends it extremely." ~ William Penn