If all you're looking for is a marina to haul and block your boat for the winter, I would just start dialing with your fingers and getting rates from those in your target area. The smaller marinas
are likely going to be less expensive, as that is their draw against larger facilities with more amenities. That said, smaller yards can generally be subject to more theft and less supervision.
Once you find a handful of candidates, ask around in forums
to see if anyone has experience with them. While hauling a 35' sloop
is a pretty straightforward affair, you want to make sure that the yard you choose has a good record
If your boat needs work during the off season (and what boat doesn't?), make sure that the yard allows owners to work on their own boats and find out what their rules are and the envinromental regulations
that they hold to. If you need specialized and/or major work done, you'll be better served finding a marina that lets in outside vendors and is in an area where there are good quality services.