02_21_2022 - Update: Hello folks; with the break in the weather here I was able to get back out and finally get the relay out for testing as well as doing the 7-Pin mod.
Here are some images to help those real 'color-by-numbers' guys like me.
The relay is held in with a bracket that is inserted into the far side (towards firewall) of the relay. Given the age of the plastic, I didn't want to try and compress the tab in the relay case to get it to release from the bracket so instead I unscrewed the two 10mm nuts that hold the adjacent relay (it was blocking access to the nut that is holding the CDL relay) and the CDL relay brackets. See image below for context. The firewall is to the right.
Once the two nuts were successfully removed, I got the bracket and relay back onto the bench for testing. Here are three shots showing the relay case (for those that need the part number), the end of the relay that corresponds with the graphic in the FSM, and the internals of the relay showing the actual relays and diodes.
Once I had the relay inside I followed the FSM testing procedure. I have continuity between pins 1&2, 2&4, but when I tested for continuity across the diode at pins 6&7, I had super high impedance (over 570 ohms when leads were oriented one way relative to polarity, and then nothing when they were reversed). So I moved on to the battery positive voltage tests. I do not have continuity between pins 1&3 when battery positive is applied to pins 5&6.
So, I'm not an electrician or a mechanic (I'm an architect) but I do know my way around circuits and multimeters fairly well.
Can anyone on here see anything I've messed up or does the collective mind think that my relay is shot and needs to be replaced?
The only thing I have left as a full Center Diff Diagnostic is 1: to apply 12v power (via a 9 volt battery in series with 2 AAs) to the motor actuator and 2: to test the continuity of the neutral position switch and the low position switch.
Thanks for anyone's advice on this. I don't mind replacing the relay but I'd like to avoid that expenditure if possible.
Cheers!