2003 Jeep Cherokee heating/air conditioning

The heater on my Grand Cherokee has seemed to stop working. It has the fancy system. Automatic dual temp control, etc, When I try to turn on the heat, or set the temp control higher than the current temperature, it still blows cold air. The AC button is off. When I parked the car after driving a while, there was a small puddle of water under it like when the ac has been running.

I have had the car since it was new and am very famiiliar with the varied settings. I do not believe the controls are in the wrong position.

Is there a simple test; a simple switch; or is this going to be one of those "electronic brain box" issues?

It has been extraordinarily warm lately for here (Western Washington - in the 80's and 90's) The engine is not overheating. The car is garaged when not in use.

Is there something I can try before giving up and taking it to the dealer? If that is the path, what are the "worst scenarios".I am a widow on very limited income and don't want to walk into a big bill without understanding my options.

Any tricks up your sleeve that you can share?

Thanks in advance for any advice!