Dodge Ram Engine Replacement

I have a 2001 Ram with a 5.2 v8 that I just had to have the engine replace, after only 78k miles. Is it possible that with the engine failing due to a main bearing going out for the transmission to be affected too?

My vehicle now has a hesitation in third gear, and will stall if I put it into reverse.

There is no direct connection on those two problems, but when the new engine was installed, the mechanic might have hooked up something incorrectly, or there may be a vacuum leak on the engine, or the throttle position sensor is not adjusted correctly.