I’m not sure the dealer see’s “sucker” on your forehead. A new thermostat and hoses isn’t a bad idea for someone who really doesn’t want to have a problem on the road.
Feel the upper hose running from the radiator to the motor. It is exposed and you can feel most of it. You are just felling for a “spot” that feels softer, or easier to squish, than the other areas along the hose. A soft spot indicates the hose maybe coming apart from the inside out and hence the softer area. This is not a fool proof test, but it can help find a bad hose.
The bottom hose is hard to get to unless you get under the car and reach up. Heater hoses are smaller diameter hoses that you’ll see disappear into the inside of the car at the back of the motor on the passenger side. There are AC hoses running into the inside of the car in the same general area.