I don't know about the water part, but I know that some older Macbook (pro)'s had problems with wire wear due to bad mounting mechanics for the hinge. Laptop screens are constantly closed and opened, so the cables inside the hinge are continously moving, pulled on etc... This could cause a display to randomly stop working. It's also possible your backlight stopped working, you can try to shine a torch through the Apple logo and see if you get an image on-screen.
English: So if I understand correctly, the flashlight doesn't work? Could be that the connector is damaged, or maybe it's a bit loose. French (google translate): Donc, si je comprends bien, la lampe de poche ne fonctionne pas? Peut-être que le connecteur est endommagé, ou peut-être un peu lâche.
Maybe try to plug in the old drive to see if that works. If that isn't detected either, there's a large chance it's the hard drive cable. Just to be sure; have you tried resetting SMC / NVRAM? Doing this can perform magic sometimes!
I don't know how the hardware problem can be solved, but your sound will probably work under bootcamp, as Windows allows you to switch devices even when they're not plugged in. Not ideal, but probably one of the best temporary solutions. As for the jack, it must be possible to de-solder it, but I would let an authorized repair shop do that for you. Next time: ALWAYS unplug the battery! I learned so the hard way with my MBP 2012 Retina blowing up on me while I was working on it :/
There's a chance something has been blown up due to overcharge or incorrect voltage/current control in one of the circuits. You could try replacing the Magsafe connector board, but as the macbook also doesn't work on battery, you're probably best off letting a AASP (Apple Authorized Service Provider) take a look at your machine.
For a full screen replacement you're probably looking at 20$ dollars, how to replace it, you should look that up on this site, if it's available. If not, there's probably a tutorial on Youtube or the rest of the internet somewhere.
Thanks for the answer man, after a lot of digging around and comparing cables, I soldered the loose cables to a new connector, but the screen still doesn't work. The macbook starts up with the Chime, but the fans are at full speed. The screen goes from a dark-green ish non-powered colour, to a black colour. Shining a flashlight at the screen showed nothing. What could be wrong? Is it worth it to buy a new inverter cable? Or could the logic board be bad? By the way, we're talking about a 2006 Macbook Pro with a 2.16Ghz Core 2 Duo. A1211