Need ''''survey on the hard'''' advice
A good surveyor should be able to spot agregious deficencies during the land inspection. The spar and sails can be inspected there as well and a creative water source can be rigged up to run the engine as wellas an oil sample which would tell you alot about the condition. You will probably only have minor points if any come up during the sea trial and can place a clause in the contract about re-negotiating the price after that. I would think you will have a fairly good idea of the boat prior to launching it.
I am in a similar position in that i live in SW Florida and I''m finding boats in the NE that I might buy. It''s a difficult position with a bit more risk but with a little creativity you''ll find an acceptable solution. Remember, you can put anything in a contract that both parties agree upon.
Also, ask the surveyor what is customary in that area for someone buying a boat during the winter months...I''m sure he''s come across this before.