More details about what's not working would help.
By "video screwed up", do you mean the display on one laptop doesn't work?
If so, are they the same model? If that's the case, then swapping the screen's quite easy, and Dell are very good at supplying detailed online instructions for how to disassemble and reassemble their laptops (I've done this quite a few times) - name the models and I could look up the instructions for you.
If so and they're different models, it's a longer shot, but there's still a chance the screens may be compatible if they're not too far apart in age.
Otherwise, buying a whole replacement screen for most models can be fairly inexpensive nowadays (I've had luck with secondhand ones), and it's one of the easier parts to physically replace.
Alternatively, it could be just the inverter that needs to be replaced. Doing that is a little more of a challenge, but I've done it a few times. A replacement inverter's quite cheap, so if I'm ever in doubt what's gone wrong with a screen, I'll try replacing that first (if it ends up not being the inverter at fault, I at least have a spare for the next time something goes wrong with a display).
I'm not optimistic about the water-damaged laptop - with the Dells I've known, any serious amount of fluid spilt on the keyboard will find its way deep inside, and unless you managed to turn it off immediately and dry it out for a good long time, then it's likely irreparable (though some parts may be OK for spares).