re: ports etc.
We've got a HL-35 with the same Beckson ports. You can go to the Beckson web site and see what they have for accessories such as the rain shield that was mentioned.
If the screen or the plastic ring that the screen is attached to isn't installed that will make it easier to leak. I don't know what it is but it is hard to make the port leak free if it is opened regularly. The neoprene gasket apparently looses it's flex quickly and you can't buy a pre-made gasket. It is sold by the foot and you have to use super-glue and make it up yourself. Dumb! Why can't Beckson sell them pre-made?
One solution is to open the ports as little as possible. If they are kept closed after awhile, with the proper knob tightening, things will seal up. Once it is leak free just leave them alone.
If you need air use the hatches, they're much better anyway, easier to operate, and get a lot more air in. We bought a bug screen from the chandlery on this web site for the forward hatch and it works great.
Keel: I've got the shoal draft keel on our HL-35 and it does very well but then it's probably a couple inches deeper IN PROPORTION to boat size than the 37. I also have a feathering prop which makes a big difference in how well the boat goes to weather. If performance going to weather is important to you then by all means get a low-drag prop because it makes a BIG difference in how well the boat will sail, performance-wise.
Over time a low drag prop will pay for itself in less engine wear (you sail more and motor less), less fuel consumption, and you'll enjoy sailing more (don't know how to put a price tag on this but who likes to sail a slug?).
Leaking washers on engine diesel lines: Yanmar says to install a new copper washer whenever the banjo fittings are opened, and I guess loosened. This is to maintain air-tight seal. If there is a problem with other fittings then perhaps someone has cross-threaded them. My 3GM-30F is 20 years old and I don't have this kind of problem, so I don't know.
Corroded quadrant: The quadrant is made of aluminum and it isn't anodized and the fasteners are stainless steel. Unless one uses an anti-seize compound these two metals will corrode which is what happens here. If the fasteners are not properly protected they will shear apart if you try to loosen them. If this happens then just buy new fasteners, apply Lanocote or something like that, put them in and it should work good for a long time. Another thing you can do is powercoat the quadrant. My brother-in-law did this for me in his plant. Nice!
Aluminum and stainless fasteners: Other problem locations are the Edson helm where the binnacle attaches. Those four bolts can easily get corroded into place. Edson has replacement screws with a special coating on them. This is only good if you can get the old ones out, though, or drill and tap new holes. Some furlers have Al-Fe fasteners and the same goes for the stainless screws holding down the winches, sheet stoppers, and anything else. But then that's true with any boat made, except for maybe a wood boat.
Gelcoat cracks are a common cosmetic issue. That does not mean to imply or infer they are ONLY cosmetic - a surveyor will be able to distinguish if they are or not.
Wiring: Boats are in a wet environment which is hard on copper. The wiring back then was not tinned and was often the minimum size. Depending on how many additional loads have been added to the electrical system over the years, and how well the previous owners have done the upgrades, it may be that the charging and battery systems need to be resized.
The icebox had minimal insulation but you might be able to increase the thickness using closed-cell foam in a can. Keep in mind, though, the stuff expands. The existing thickness can be checked, subject to accessibility, using something like an ice pick.
Holes in the structural grid: Be leery of any holes that owners have added in the structural grid. If they are large, or in the wrong place, this can be a problem but a surveyor could help. This would be true for any modern boat with a grid.
Otherwise, it's a20-year old boat so you need to expect some challenges in maintenance: fiberglass, gel coat, diesel engine, sail, bottom paint, etc.
The HL-37 has a very nice interior plan and the boat looks esthetically pleasing from the outside. In fact, I think they look really good. If your wife approves that's a major consideration.