Recently had 2002 Diamante heater core repair- had to take dash out and steering column- now gear shifter is stuck - will only go into neutral and drive- key will not come out of igntion. Any ideas?

 

Open the center console again. I'm willing to be that the moving parts were put back correctly (alignment). Just follow the shifter lines.
I've had this issue with my old auto too and all it was, was the shifter's lock (moved by the button on the shifter handle) was getting stuck on the steps...you'll see what I'm talking about.
Just take the center console out and move the shifter around (try to anyway) and try to find the obstruction. You'll have to do this with the key in but motor does not have to be on.