Rud,
I hope by now your issue is solved I had a similar instance happen on my '94 sl320 all of the same symptoms, I found that I had blown a fuse that controlled the turn signals/all things at the central mirror location ie:interior lights etc. Replaced the fuse and everything is ok driving along and I hear a sizzle and loose all guages and signals. I get where I am going and can't put up the top. On my return home I start to investigate the sizzle I heard and discover a loose screw under the header lamps at the rear view mirror it had fallen down and must have jiggled it self around until it popped the fuse (it is only a 8amp) my driving must have continued to jiggle it and convinced the car that the battery was too low to operate the top. After getting everything sorted out and replacing another 8a fuse I went for a ride so I could run the car at 3k rpm for an extended period, when I got back to my home the top worked like a champ as did all the lights. I only have to find the proper retaining screw for this area and I am done. I find that taking a step back and thinking it over works pretty well 1or2 beverages always helps. I could go on and on with the self diagnosed problems I have fixed and can't imagine the cost I have saved. Also the engine wiring harness is not as daunting a task as it seems I replaced mine in about 2 hours dealer quote $2500 DIY all in I think $650 I bought the parts here and found a good level of instruction here as well (search) my sl is a 6cyl. not an 8 but I still think an 8 is not that difficult.

Regards,
KD