Reading Codes on 1995 E320 - A Brief Summary, please!

[RLGDiesel]

I need help pulling codes from a '95 E320 M104. Although OBDII was not mandated until 1996, some forum members have suggested that '94-'95 Mercedes models (SL?) have OBDII. Other threads point to a small LED box built on the firewall. I have noticed this box and the small button under the #2 position, but I have no idea how to read the codes and count the "beeps." Additionally, some people have stated that $1.29 LED piece from RadioShack would be helpful in reading DTCs.

Could someone share a brief summary of pulling codes from a '95 E320 with me?

Thanks in advance!