Having recently changed out a LCD display on my 87 SDL:
If you have a telescoping steering wheel move it all the way out, pull the instrument cluster with the appropriate hook tools.
You can then tilt the cluster upward and to the left or right, using a short or stubby Philips head screw driver you remove the two screws holding the LCD display in place. First the screw on one side the tilt the cluster the other way and get to the second screw on the other side. The screws are approximately three inches apart one on each ear of the module about one inch to the right and left of the electrical connector. you will be holding the screw driver in your hand with the tip facing towards you. You will in essence be attacking the screws from the inside of the dash perspective. Itís not as hard as I'm describing! with the two mounting screws removed you can grasp the electrical connector and pull the module back towards the dash about three inches and itís free! unplug the electrical connector.
For the next step it is important to have the proper tools as the screws are very small and the heads are easily stripped, not so much during their removal but as you rescrew them back in during reassembly. You want the largest tip that will fit the screw head as a too small tip will move around and slip out of position and there is not much meat on these little screw heads. I used a screw driver that I had bought at SEARS for $2 that I checked for a perfect fit. I just brought the module with me and went through the ones they had in the rack!
The module is held together by four very small Philips head screws, remove these four screws and you can pull the plastic housing apart exposing the circuit board. I have examined two types of innards to these modules : the older type uses a full size circuit board with discreet components and the newer type has a much smaller circuit board with VDO's proprietary surface mounted IC chip. But there is a separately mounted "grain of wheat" bulb on either. For the old style unit you can see the bulb near the back of the LCD itself, on the newer unit once you open the case the main body has only four wires traversing it, the circuit board is much smaller and mounted vertically at the front of the case, you have to remove two additional screws to free this smaller circuit board.
Once you gain access to the bulb you remove it using a soldering iron and replace it and re-solder the new bulb in its place. These very small bulbs "grain of wheat" are available at Radio Shack at about $1 for two. I don't have the part number but you can just take your module with you and compare to get the right one just make sure its 12V. Hey at least you don't have to jack up the car and crawl underneath to do this repair, Good Luck!