I’d say if you cannot see anything obvious from the bottom of the mast, and use some binoculars to do the check, then don’t buy in anything on the off chance that it might need changing. Selden parts are not cheap, and may well sit on your spares shelf for years before you actually need them. As a “for example,” a friend asked for help regarding his foresail, and while onboard his boat it was noticed that the aluminium feeder for the sail into the luff groove of the foil that fits around the forestay had come off, and the black plastic part that interlocks with that aluminium feeder would not grip the feeder. He contacted Selden in the UK who have had to put in an order to Sweden, and those two tiny parts have set him back £85, but better that than the risk of tearing his fore sail.
Possibly worth checking for wear will be the pin and gooseneck hinge arrangements where the boom and the kicker connect to the mast, and the black coloured aluminium moulding at the foot of the mast that it sits on and which is located on the cabin top should be checked for any obvious cracks.
Apart from that I’d say that most parts are relatively easily accessible and changeable even with the mast up.
If you have any problems with your wind speed indicator, then it could be worth looking at a wireless system rather than replacing the wiring.
Changing the wiring for nav lights, deck light, fog horn etc., as you have already planned from ordinary copper to tinned, is definitely a worthwhile exercise.
While the mast is down take time to measure the length of the shrouds from bearing surface to bearing surface and make a careful note of those lengths and wire sizes, and also the sizes of the bottle screws. Also while the mast is down it might be worth while removing anything portable for security reasons to inside your cabin. Yes, it’s a pain in the arris, but there are lightfingered people around, though sometimes it works in reverse as I had a new windex fitted to my mast on one occasion when it was down. I don’t know who fitted it, but thanks to whoever did it !! All the masts had been laid across a series of trestles and someone mistook my mast for theirs, so thanks again, it was appreciated.
Before your mast comes down take photographs of the wiring connections where the wires are joined within the deckhead area inside the cabin, and record what goes where so that you are not left with a myriad of wires to connect and you’ve forgotten what goes where when it all goes back together.
Spray some WD40 or similar over the threads on your bottle screws so that hopefully they will undo easily without the stainless threads smearing and leaving you with the cost of having to buy new ones.
