How much does it cost to fix a coolant leak?

I bought a 2005 Dodge Magnum 5 months ago, car was
running fine no problems up until a few days ago when I
got a oil change a leak showed up. I’m not an expertise so
I was back and forth taking my car to the lot as well as the
place that did my oil change, also taking my children to
and from school. I had a pressure test done and it looked
like a rainstorm was underneath my car. I was told I had a
leak in the back of the engine right next to the
transmission, I couldn’t drive it hardly nowhere without it
overheating instantly, When I found out how severe it was
the car started cutting off and wouldn’t come on until it
cooled down well now thick white smoke is coming out of
my exhaust system when I start the car and drive it. Is this
repair worth me paying for? And what is the estimate of
what I will be out of to fix it?