the car had overheated , never doing this before , and at the same time the transmission started messing up , as in didn't want to shift into gear , i know nothing about cars but was told that the radiator must have went bad , could that be it?
there is transmission fluid in the radiator and coolant in the transmission line on 2002 Dodge Neon
YES THAT SOUNDS RIGHT.
Yes, unfortunately, there is a transmission cooler in the bottom tank of the radiator that failed. This caused the transmission fluid to mix with the antifreeze and vice versa. You will need a transmission and cooling system flush and depending on how bad your Neon overheated...you may need a heat gasket replacement.
I agree with both #1and #2