In my search for the diagram I came across a note on this problem.
Apparently there is an issue with these and it isn't entirely the shifter at fault.
The shaft that goes into the transfer case can seize up due to corrosion as well.
In the picture below you will see a shaft. (the picture is out of a Dakota, but yours is similar.)
The top where it is attached is the bottom of the shift lever.
The bottom is where it is attached to the transfer case.
Pop one end of the rod out.
See if the shifter moves easy or not.
If it does, then it is the transfer case shift shaft.
You could try multiple applications of penetrating lube and work the lever to try and free it.Linkage
Sorry I did not come up with this earlier. I have not seen it happen before on these.