Disconnect the cables at the transmission and then try
moving the shift and select arms through their motions.
They're internally detented, it's pretty easy to feel if
the tranny's shifting correctly. If it won't shift like
that then the tranny's likely toasted. If they will shift
properly then go up forward and pull the shift surround,
the screws for it are in the ashtray bays. That exposes the
cables and you can check to see what is blocking the shifter
mechanism. With the cables disconnected at the rear the shifter
should be free to flop around through it's entire range of
movement.

JazzMan