Well to be honest you said this was a water damage, so lets run down some things I would do. So i will assume it was submerged. First thing will be to remove ALL moisture. And water is not always clean. So find some 90% alcohol. wash the entire board (no batteries) in alcohol, submerge it if needed. Now you need to dry it out. Heat is best, but let the alcohol evaporate.
Do not wash touchscreen.
To get all the moisture out, the right way is to use a 100deg oven. No plastics, just the mainboard. Capacitors are the thing that can be damaged by heat, so thats why 100-125deg MAX for drying. I have seen people put a lightbulb in a metal tool box with a pcb to make a tiny oven.
Without doing that to ensure that water is gone, you could be chasing ghosts. This is a good project, and if you bring it back to life, then you should be proud -- if not then lesson learned.
Keep asking questions -- maybe this thing will live. I will see what i can find for more complete schematics
