I wish I could be of real help on locating the switches. My '66 W111 coupe doesn't have them.
Kroil is a highly ranked penetrant. You'll find it at places like NAPA, and maybe your local hardware store. PB Blaster is another good quality penetrant. WD-40 is typically very poorly ranked, as it was never designed to be a lubricant, or a penetrant. WD stands for water dispersant, formula attempt, number 40. It was designed to be sprayed on the wet electrical components in the military. It's also a pretty good hand cleaner.
If you have enough access to remove the switch(es) from the horizontal position, and stand them upright, that'll help the Kroil creep down in. If you can wiggle the pin side-to-side, that will also help the capillary action and get the Kroil to seep in. You may find if you let it sit for a day or 2, keep wiggling the pin, and applying small amounts of penetrant, it will free up. Acetone mixed 50/50 with ATF also makes an outstanding penetrant. Heat from a hair dryer can often help when a pin is stuck inside a switch, due to the varnish residue left behind when original lubricants or grease age and fail.
Last, or maybe "another" option, is to see if you can get the switch apart, even if you had to JBWeld epoxy it back closed. If I saw a much better photo of the switch, maybe I could help with figuring out how to safely get it apart. I've never seen one.
Do the diagrams on the niemoeller.de website show anything?
