1995 Nissan Maxima Hole in transmission pan

I was driving while a metal block on the road hit from below and punched a hole in the transmission pan. I am not sure how hard was the impact and whether anything else was damaged. Car was at about 45 mph. Car was towed to Aamco transmissions who told me that computer diagnostics didnt show any code and they had to open up the transmission and may have to rebuild it for $1400. Now they are saying that fine metal particles went into other parts as well and apart from rebuilding the transmission, they have to fix the torque converter, solenoid valves and flush the radiator too totaling $3000. This happened 200 miles from my home in another state and the car is still there.

I want to know whether a small hole (about 1 inch) can cause so much damage to so many parts. And whether work on so many things is really required. I am quite sure that they know I am from outside and have to get it fixed so they are trying to do as much work they can. I will have no way of saying what they did and what not. I was under impression that only changing the pan and refilling the transmission oil should fix the problem.