If you're just trying to undo the linkage, just pop the linkage out of the bushing on the trans side.
On the tranny linkage, pop the linkage off the end of the arm. I don't recommend trying to undo the nut holding the arm on. I've seen a few instances of the threads twisting off instead of the nut coming loose and replacing the shift rod is a major effort.
So what are you trying to accomplish, btw?