I did not need the tool for my 400E. I just finished installing white gauges and replacing the bulbs just now. You could use a coat hanger and cut off the ends. Here is a link to taking out the instrument cluster and a illustration for using the coat hanger method. I did not need to use it. I just pulled the bottom out and pushed out the instrument panel from the inside. There are three different bulb sizes that I needed. You might want to bring the size to the nearest Pep Boys. The bulbs with the socket attached will cost a lot and come as one piece. BTW, there are like about less then 20 bulbs in all. Also, the instruction for removal may vary from model to model in the W-124. Mine was different but, not hard to figure out. This will just give you a basic outline on the procedure on how to do it.
Instrument panel removal and install