First, buy the boat! $700 is a good price on anything that floats.
And if you find a newer boat down the road, sell this one and buy the newer one latter. You will have been sailing the whole time so you are better off buying now.
The leaks- does it freeze where the boat was kept. If so, then the leaks are probably in the wing tubes. Water left in the tube freezes and expands and splits the tube. Anything is possible to fix, so don't worry too much about it. Install a hatch and glass the tube from the inside of the boat. To have a quick check, take out the wings and fill the holes with water. If it drains into the hull, then you have your answer. If it doesn't leak there, then the fastest way to locate the leak is to pressure test the hull then soap it up and look for bubbles, but before you go to all that work, the most common leak is actually the drain plug housing. If the drainplug housing has not been resealed with silicone in the last few years, then this is probably the leak or at least one of them. Take out the two screws, clean off the old sealant and replace it with new sealant.
As far as trailering goes, do not take the boat apart. Add a longer tongue, a mast support, and two crossbars (4x4 wood will do for short trips). Doing this may also allow you to carry the laser under the 17 at the same time. Taking the boat apart is not a good solution. The other option is to borrow a trailer to take the boat home and to the sailing spot twice each year. I'm sure someone would lend you a trailer.
