Good luck with your boat
We have sailed our 1973 Grampian 26 for 17 years in the Montreal region.
My main concerns have been possible leakage of water through the chainplates, which come through the deck, to which are attached the shrouds. The chain plates are bolted to blocks inside the hull and are not easy to inspect. I wonder if these blocks can rot leading to failure. It is easy though to chaulk this point on the deck.
If you have the aluminum toe rail water always accumulates on the deck at the low point next to the jib sheet winch boss. This looks a mess. The original design had a wooden toe rail and at this point there was a gap for the water to run off.
The rudder on one G26 we know regularly got saturated and had to be rebuilt. Check it for cracks and remove rudder and store indoors in winter possibly. I have a bronze rudder shaft and bushings. The bushings are now worn causing the rudder to vibrate slightly. These bushings cannot easily be removed. Some G26s have a "nylon" bushings which probably could be replaced.
The teak cabin top hand rails become thin and weak especially if owners like to sand and varnish. I see them often replaced. I broke one. Similarly the companian way teak becomes thin.
I have a couple of soft spots in the cockpit floor.
Be very careful if you unstep the mast for winter. Do not twist the aluminum casting at the foot of the mast. It could break.
The window rubber gaskets perish with time.
None of these points ever gave me any real problems so far. So I would look after your boat and it should do well.
I have an outboard and sail in fresh water. One neighbour (not a G26)with a saildrive sailed to the Bahamas. The foot corroded through so be careful in salt water and ensure you have the proper galvanic protection.