You need a torch, a couple of jewellers screwdrivers and a set of hex keys (because I have forgotton the size).

Shine torch in right hand side of centre vent, locate and remove setscrew with hex key. Look into centre vent top and bottom right and left and you will see 4 small catches, taking one side at a time stick a screwdriver in each and sort of squeeze together (on the top one you put down pressure and vice versa)at the same time ease the vent assembly out a little and then repeat other side.

Once out the lamp replacement methodology is obvious.

Reassemble by pushing vent assembly back in, locate setscrew and tighten.

Hope this helps
NormanB

__________________
NormanB
230 TE (W124) 1989 with 153,000 miles on the clock - hoping for at least another 100K