Finally got up enough nerve to replace Engine Control Module (or Ignition Control Module). Reason for hesitation in replacing...afraid of disappointment if problem not resolved after spending $700+. "Plug and Play" it did, engine started on first crank and now runs perfectly.
I want to think the forum for helping me with the problem I was having with my 92 500SL. I especially want to thank M.B.Doc for his "Plug and Play Advice" and JimF for a better understanding of electronic circuitry from his website.