[Howard Klepper]

There is no point to the trash bag and wet sponge thing, because there is no use in overhumidifying, and that is what you would be doing in a saturated, 100% RH environment.

The first thing to do is know what the humidty is where you keep the guitar. There are many cheap digital hygrometers. Most are about just as good as each other, so don't worry about the brand. But they can all vary from one sample to the other, so it's a good idea to get two. If they read about the same, it's more likely to be a reliable number.

If your room is below 40% humidity, that is not healthy for the guitar, and should be brought up to the ideal range of 45-50% with a humidifier. Or you can humidify it in its case. That is easier to do, but then the guitar gets exposed to a humidity change every time you play it, so I prefer to humidify (or dehumidify) the room.

You can bring the humidity up a little over ideal to close the crack, but if you have to bring the humidity over about 60% to close the crack (give it a few days to a week to close up), then it is likely to open again or crack somewhere nearby when you go back to the ideal humidity. So in that case the crack needs a cleat, which will stabilize it even though it's not tightly closed. If it closes at about 50-60%, just gluing the crack should be enough, but a cleat can't hurt after you have the crack closed.

Don't use CA glue--it can mess up the finish. The ideal glue is hot freshly mixed hide glue. But if you don't have experience with that, just use Original Titebond. You can work it into a closed crack by saturating the surface and flexing the crack slightly several times. Then wipe off the excess with a damp (not wet) rag. Wait a day before putting any stress on it.

The crack along the fretboard edge is possible trouble, because it can be caused by the fretboard shrinking, which may mean the fretboard wood was not well dried to begin with. Keep an eye on it, and keep it in humidity above 40% and ideally 45-50%.

Come back if you have problems. If you are handy and like to DIY, you can fix this yourself. Also, check Frets.com for very reliable advice on repair. I'm sure there are some things there on basic crack repair.