Hi @fanxylegacy ,
The biggest problem would be corrosion and possible electrical damage to components caused by water causing current to flow where it shouldn't, because the battery was not disconnected from the systemboard as soon as possible after it got wet.
If the power was turned on while it was still wet internally then more damage could have occurred.
When the device eventually dried out then the only problem would be the ongoing corrosion.
The device has to be opened and cleaned using Isopropyl Alcohol 90%+ to remove the corrosion.
Electronics Water Damage
After so many years it may be impossible to fix as the corrosion (which doesn't stop) may have destroyed some components.
Also no doubt the battery would have to be replaced as it may be irretrievable.
You won't know the extent of the damage until you get it open.
Here is a link to the ifixit Nintendo DS Lite guides which may be of some help
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First two ones are the Y wings.
Guess their edge are too blunt
And these are all What I can use
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This bolt is A Freakin Problem....
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