The first thing I'd do is replace all the fuses. Don't even check them, just toss them and fit all new fuses. If you get the fuses through the FastLane link above it'll be under $5 (plus shipping) for all the fuses you need.
The 105C/115C switch is probably the only 2- or 3-pin coolant temp sensor near where the upper radiator hose meets the engine. I doubt you'll have trouble finding it if you're the least bit familiar with automotive cooling systems. Removeing the connector (2-pin) or connectors (3-pin) will get the AC clutch engaged if the switch is bad.