I don’t know about the bushes, (I have the nylon), but to replace them, I disconnected the rear link from the transmission and the middle joint from the engine. Then, remove the four nuts holding the shifter in place. You can then pull the whole assembly back to reveal the shifter and bushing bolt through the hole in the tunnel. It is still a bit of a pain, but a lot easier than trying to get to the bolt and bushing with the shifter attached.
I do not think that bushing makes much difference to shifter vibration. It can introduce a lot of slop though if disintegrated I believe the bushing attached to the bell housing makes a big difference to vibration.