I grabbed some screen
shots of you M31 when she was for sale
in case we decide to put a D1-30 in ours :-)
Sorry can't help with a sail drive, never had one, but is there s space between the gearbox base and the drive leg top, which is now full of oil?
Of course someone could have simply forgotten it which is probably more likely.
What you do about it is tricky. If the boat hasn't moved much over the winter
I would just carry on as I don't see the seller discounting the price
by the cost of a recon gearbox given the time of year and the demand, but you could try.