It looks like a little cap that has Prestone written on it, I have a slight leak coming from there and also this other little piece that has a cable hooked to it. It goes into the firewall, I'm assuming it is for the climate control. I'm wanting to put in a brand new hose, but do I need the Prestone piece? I'm sure I need the other box thing with the cable too.

 

the piece with Prestone on it is not original to the car - it has been installed by someone in order to flush the cooling system - comes in a flush and fill kit sold with Prestone coolant - you don't need it

the other piece is the valve that lets hot coolant into the heater - when you move the heat control lever on the climate control to hot, it opens the valve allowing hot coolant to enter the heater core - you do need it