The vacuum diagram is in the CD-Rom for chassis 126. If you are serious about working on such projects, this level of info is imperative.
It would also show you how to remove the glovebox and lower dash panel. Basically the panel is held with 4 screws and the glove box comes straight out after pulling all the clips out. Remove the light and disconnect the wires.
Bosch Master, ASE Master, L1
33 years MB technician