No need for apologies. It can be intimidating the first few times.

You're right on with testing voltage. Set the meter to read in the 12v range. Touch the black probe to bare metal, and the red probe to the wire. If it shows 11-12v, you're good. Turn the ignition off, and it should drop to 0. As geezer said, the red/black wire should always show battery voltage, because it's the backup wire.

I'm repairing a spare dash harness to add a radio back in to my truck. It's sitting on the floor in my basement, so it's easy to get photos of. Let me know if you need any help.