For me, the freakiest part of taking apart an interior is yanking and pulling on various panels, hoping nothing will break.
Lots of the panels on the 4Runner are held in with pressure clips. I'm not sure if that's even close to the correct term, but these clips aren't threaded or otherwise locked into place. They have surfaces that exert pressure on their respective sockets. That pressure holds the panel in place.
There are, however, about a half-dozen bolts that have to be pulled before you can yank the various panels. Failing to remove the bolts ensures that you WILL break something. This is where the online article I posted the link to came in extremely handy.
Today's head units are buried in the dashboard. After several panels were pulled and set aside, I was finally able to undo two bolts and pull the head unit.
Since I was merely doing an R&R (remove and replace) on the head unit, there wasn't any wiring to figure out. It was merely a matter of unclipping the connections on the expired head unit and swapping them over to the good one.