The speedo cable might be shot, see if that is why it's not working.
For the radio, disconnect the rear speakers in the trunk and see what that does. If they got wet from the trunk leaking, then chances are they shorted. When that happens the front ones won't work either. Try it out, see if the front at least work. If so, then it's a short. Either leave em unplugged and just have the front or replace them.
The door bell thing, it's common to not work. Mine doesn't either. I have replaced mine twice from the boneyard, and notta. Think it's just a piece of crap item and not worth messing with.