katcat

If car is above 100k km, better change than guessing. It supposed to be change after 90k km - 100k km, wherever you have time and money to change it.

Sell the car to me and i will drive w/o AC. 20k cash tomo. Please PM me if interested.

Black rubber hose coming from engine towards the radiator has the thermostat in the beginning of it. Its quite obvious location on top, nothing hidden.

I believe you havent used the specified Transmission fluid that could cause the slippage when hot.