Coolant leaks inside the car and passenger side

That's a typical symptom of a leaking heater core and a plugged air conditioning condensate drain tube. Replacing the heater core involves discharging the air conditioning refrigerant. That can be very dangerous. Beyond that replacing a heater core is a real big job and not one for the average do-it-yourselfer to tackle. If you think you're up to the challenge, get a copy of the manufacturer's service manual and read through the pages of instructions, then decide if you want to attempt it.

There aren't any hoses inside the car, just metal pipes, or, in the case of a lot of GM vehicles, plastic pipes.

The heater core is the only thing that can leak inside the car.