87 Chrysler 5th Ave lurches and stutters when accelerating up to speed?

We just recently (less than 5k) put a new transmission in the car. But it was recently stolen and ever since we've found it, the car has been stuttering and hard to accelerate. It happens from a stop or even while speeding up on the freeway. And now once it gets up to 55mph or so it sometimes shakes a little. This car was in great condition before, and has roughly a 100k miles on it. We know the person hit something because now the hood won't close all the way and there is a nice dent on the back rear panel. The car is to old to have the test done that reads the engine to tell us what the problem is so we don't know where to start. Any help is SUPER appreciated! Thanks so much.