The light pipes are held down by a white cover that is molded onto the housing in several places, I can't even budge itand I don't see one in the picture of the old version housing (above)
The pipes travel from the outside rear into the inside through some hidden passageway and looks like its very much a part of the housing assy.
Just find a complete housing and swap the instruments over. I think you should hold off for a new version if you ever plan on driving much at night

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!