I replaced both sets of shifter bushings on my 300E and 560SEL. The new bushings are not fun to install at all. Besides the tightness of the space, especially the rear one attached to the shifter, the new bushings does not go in the hole just pushing it with your thumb even with the use of lubricant. Can't get much leverage at all. The front one is not as bad because you can remove it and work it on a vise.
What I did was use 3" long bolt and some flat washers and a short socket ( almost the size of the bushing). Used it like a small press. It worked but it still was a pain. A couple of times, the corners around the hole cut onto the plastic bushing. Make sure to smooth them out. Good luck!!!