Does anyone know what is the procedure to get to replace the lamps behind the clock and the left-most vent controls in the center dash?

 

your car is W126, W140, W220, or Jaguar?

pull out the instrument cluster to replace clock bulb.

the vent also must come out in order to replace the bulb.

 

95 S420 per previous post, so 140. Don't know about clock, but centre vents you need first to pop the glove box lock. Set key half way between open and locked (45 degrees). Push 1.5mm diam, 4cm long pin down into hole on side of lock cylinder (Mercedes have a tool for doing this, but it's probably not necessary). This springs the lock which can then be withdrawn holding the key (keep the key in the cylinder to avoid the tumblers falling out). Unscrew the lock unit from down the centre of where the cylinder used to be (1 screw). Undo the upper central glove box (two screws at rear) remove glove box. Unscrew vent unit (2 screws at top). You can then fiddle with the vent unit where it is, or undo the wiring harnesses (2) to remove from vehicle.
Regards