Re: T-case stuck in N - won\'t go into any other gear!
Had the same problem, and I'm not the only one. What happens when the "sheet" (which is really a rubber washer, not a sheet) wears out is that the shifter drops down a little, just enough that it is not engaging the two side "pins" in the housing that keep it alligned. Now when you try to shift, it is twisting slightly, just enough to try and move both selector rods in the T-case simultaneously, which they won't do, hence you get stuck in Neutral.
The advice give above works. Get the stick out and move the rods manually.
Or try this. As he attempts to shift, he should hold the lever up a little, and make sure that he doesn't allow it to rotate. He mey have to actually try to rotate it a little in the opposite direction to get it to turn enough to engage only one rod.
Tell him to relax, it is not a big problem.
Otherwise, no amount of pulling and pushing on it is going to get it to shift, don't fight it, fix it.