What are you looking for?
- A project boat? - Cheap but can be resuscitated, needs multiple repairs that may require time/effort/skill, "bones" need to be solid
- A functional boat? - Shows its age, but no major repairs/replacements needed, except new sails and/or running rigging
- A fully restored boat? - Everything is optically and functionally perfect; you'd haggle over any scratch
The same goes for a trailer. Substitute tires for sails and running rigging as the "consumables".
These boats, DS1's even more so than DSIIs are eminently repairable. Some stuff like standing rigging should be replaced periodically, other stuff, like running rigging and sails are true consumables (their lifetime is measured by use). Foils can be rebuilt or repaired with moderate expense / effort. Fiberglass repairs are fundamentally not hard. Painting a boat will take effort, care and for best results, also a bit of skill. If that's not you, and you need the optics, you know what not to buy.
One exception is the mast. Hard to ship and hard to fix - don't buy a bent one. Don't by a DS1 with rust along the cuddy opening: there's rebar(!) there, and if that starts to rust, the repair is involved (but doable).
Tabernacle is a drawback to anyone wanting race competitively as the mast behaves differently. For more casual racing or cruising, not as much an issue. Know what you want.
Ask for a test sail, if the boat is in the water.