I recently had a used engine and transmission.

I recently had a used engine and transmission put in my car, when I got it back transmission fluid was leaking out not alot but a saucer size puddle. I drove the car about 100 miles in a 3 day period and on the 3rd day I went a short distance and when I stopped the water from my radiator was leaking so I topped it off and was driving home when I got off the frreway my car all of a sudden my tires were smoking from skidding because my car just stopped I guess it seized but then drove far enough to pull to the side of the road. When we checked the radiator it was so hot that the fluid I put in sprayed everywhere. So my question is, if it was the transmission why did'nt my temperature gauge read hot and is my car (transmission) ruined? Also the guy that checked it out said there were metal shavings from the gear box. What do I do now?