Kahooli: The wiring has been upgraded fairly recently; it's romex.
Fishindude: Correct, the ends would be nailed into lumber and probably the studs. Unless, as J Boogie suggested, the installers used a brad nailer or something, the siding won't pop off without a lot of pressure.
DoNorth: The moisture barrier is Tyvek, which, now that I look at it, has more perms than I thought. The climate is mostly cooling. That said, I've love to put rigid foam on the outside but that's a major project and far down the list.
Thanks for the videos, HipGnosis and zolotiyuruki. Those are informative and ease my mind re:cracking and blow outs.
I'm going to delay having this done until after the holidays when I have an entire day to observe. Thanks for everyone's help!