1. Quietly for sale? I suppose all boats are for sale at the right price, how much are you offering? Kidding aside, good race ready J/30s can be found for 15-25K USD. Boats in the 5-15K range usually have defects you may be able live with but if repaired professionally will offset any savings. Travel and shipping to Canada may be a significant factor.
2. Some feel the old style's wide bridge deck allows trimmers to cross work more efficiently. New style cuts down on water washing into the cockpit, helpful if you are sitting in, but you hike outside the combings while racing. Both are comfortable beating, though the old style relies more on feet than butt checks at the helm. I've sailed both but have become accustomed to the new style after many years.
That said, don't restrict yourself to boats with the new-style cockpit or you may be disappointed. They command a premium because there are fewer of them and they're newer--though the difference between a 1979-80 and a 1983-6 is less significant than how well the boat has maintained. Over the production run more interior wood was added, the galley was altered and the berth count went from six to five.
3. The biggest issue is water in the core which can be fixed, but should be determined by survey. Mast, engine, rudder, and winches are the expensive bits so be sure they are sound.
