1. Yes.

2.Well, that's the thing.
We're not going to run "volts" thru the switch. We're using the switch to provide ground to the relay, which is powered, to the lock-out, then to the solenoid.

3 Yes, when you are done, that's how it will work. Our switch with ground on it will complete the circuit.

4. Doesn't have to be, that particular relay works even if it's loose.

Check out the reverse light relay (9) on page 193 of the Haynes (the diagram is for an automatic, but easiest to read), notice the reverse switch (#11) has no power going thru it, it just provides ground to the powered relay-completing the circuit.

The wiring instructions I provided in the earlier post are exactly how I found it in the Canadian GT I parted.

5. Depends on the kind of light you have. The ORIGINAL early1800/123GT light has two terminals but they are connected (obviously)...you could go from relay-term-87 to one prong on light then from other prong on light to lock-out. Same-same.
Yes, when you bolt something metal to an Amazon, that metal is grounded. Nice thing about a car made of steel :o)

Hope this makes good sense.
Shayne.