headlight-horn switch

I have a 1996 disco I, 110k. I had a leak in the moulding / seal of the front windshield, which i fixed by replacing the windshield. Water would pour in, dripping off the rear view mirror. Now i have no dashboard light, the illumination of the heater / temperature gauge does not work, and the parking lights do not work. The headlights do work however, along with the radio, and dome lights, and all other indicator /reverse lights. Last winter the horn shorted out and was "stuck", i had to pull the fuse to get it to stop.

So i'm thinking the switch on the left side of the steering column may be toasted. And, am guessing the water pouring off the rear view mirror onto the center console might be responsible for a few things.

Other than checking the fuses, how can i go about locating the switches etc. that are causing these problems. I read the Haynes manual and their electrical diagrams and am thoroughly confused.