The 1973 vintage is probably the least important factor. (Mine is a '63 DS1, just for comparison). Really, these do not age along the same curve as cars. These boats are eminently repairable and most owners perform their own work. Some come here first, for advice.
Many repairs or upgrades can wait until you've sailed the boat a few times; so there's normally not much need to spend time & money on the boat until you know she's a keeper. There are usually a few smaller things that you may need to do on boat or trailer, esp. if it has been sitting around for a while. That should be reflected in the price.
That said. The lazarette cover is cosmetic, someone reasonably handy (yourself?) could easily fashion a functional replacement - even if it didn't match in material or finish.
If what's "buggered-up" is just the frame around the opening, that can be restored and/or covered by your own (much better) version of locking cover.
Things to look for: is the rigging complete? Wires and fittings for standing rigging should be free of obvious damage or rust. Spars not bent. A bent mast is something to stay away from. It's not a standard repair.
Hull: separation of deck from hull? Major cracks (not crazing or spiderwebs)? Any deep gouges or even holes? Any sign of impact damage? Any visibly "soft" areas? All in principle repairable, but something like that could be more than you would like to take on, unless you are after a project boat. (If you are comfortable working with fiberglass, or game to learn, even collision damage from another boat might be fixed in a weekend - that's what I mean by repairable - see
Gored: crack repair).
Condition of rudder (chips, cracks, splits). Centerboard, the same, but may be difficult to inspect. Chips and even minor cracking can be repaired (DIY), unless they are asking top dollar, some wear is expected. Ideally you'd have the CB demonstrated on the water, but that may not be possible.
All lines and sails present?
The latter point is mostly so that you have a fighting chance to rig it for the first time, even if you decide to replace some or all of the running rigging. It gets really tough if you don't know the boat and there are parts missing (or extra) and you are trying to make sense of it all. Otherwise, running rigging and sails are consumables; they will need to get replaced over the lifetime of the boat possibly several times depending on usage and UV exposure. Unless you plan to keep the boat for only a couple of seasons, you'll replace some / all of the lines and the sails anyway at some point. If these are due now, you are just jumpstarting that cycle (something you might figure into the offering price, but not a reason to walk away).
Summary: if all parts are present, nothing has any major damage that would prevent you from taking her out a few times before you make upgrades, it's probably worth considering. There's some variation in condition, but that becomes a matter of price.
Not to forget: trailer. Expect to replace bearings and or tires, and to rewire the electric - that seems to be due every couple of seasons even for well-kept trailers. Like the boats, these trailers are easy to maintain yourself. I had the seller deliver my boat, which he had offered. That didn't mean that I didn't have a failed bearing a few weeks later...