I looking and studying the donor instrument tri-gauge portion of the cluster which the rheostat mount to, I noticed the same burnt wire-trace which is highlighted in the supplied links. Thanks.
This brings up another issue! MB according to other forums has had problems with the dash gauges and had replacement circuit boards available at one time. This look like a design flaw. In tracing with a meter, you can see where the wire trace gets thin leading back to the big plug connector in the circuit board. My best guess is that an excess current flow caused the trace burn. A burn makes sense! This trace provides power to the rheostat only. If a burn occurs before 12vdc is supplied or after being supplied to the rheostat this would explain the dash lights being out. My calculations (ohms law) I'm sure are off, but either 1/4 to 1.4 amps would be supplied for the dash light circuit. I think it should be able to handle a little more than that. Maybe a modification is in order with a removable fuse.
I need to use the car for the next few days, so I'll remove the panel after that for other things need to be done also.