There's decent room to work in a 126 SD. Set the lever in D, remove the bolt and nut (2 10mm wrenches, there's a tiny washer on the nut side) holding the selector bell crank in place, remove the clip at the aft end, pull the rod and bell crank aft and out. There a MB tool to press in new bushings but I do okay with channel pliers, Sil-Glyde, a big washer (to push) and a 19mm socket (to receive). Installation is the reverse. Note which hole in the bell crank the rod went through.

Sixto
83 300SD