Well, went back out to venture a finagle with some metal shims. Decided to try to pop off the plastic front trim piece first...hmm seemed pretty stuck, pulled hard on the side of it...plunk, there pops the head unit out of the metal sleeve. Huh.
Well no problem, let's pull it out. Couldn't get the piece of plastic trim off, but maybe it'll just slide right..... ah hell.
Whatever...unscrewed the little latch piece, set it aside. The rest of it slid out no problem.
Upon full removal, I ran into what I KNEW would be my next issue...the big adapter with all the important cords is obviously not transferrable between the old one and the new one. Thank goodness someone marked "LEFT SPEAKER FRONT, RIGHT SPEAKER COCKPIT", etc. The wires should be fairly easy to work with, but I need electrical tape. Or wire nuts? So that's on a brief hold. I did check and found that the new head unit will slide into the metal sleeve no problem. I may have to use screws or something to secure it, but that won't be an issue.
Two things that scare me a little - when I stuck my head in, I saw what looks like mold that started growing above/behind the never-moved head unit (confirmed with PO I'm the first to mess with this since the Previous PO [PPO?]).
Is this a spray-and-scrub job or an indication that further investigation needs to be done? I tried unzipping the headliner and ran into issue #2...the zippers on both sides seem absolutely frozen. I didn't yank too hard for fear of busting a difficult-to-fix zipper.
So, to summarize, at the end of tonight's visit I have the following issues/questions:
1. How best to splice the boat stereo wires to the new stereo adapter? Wire stripper and electrical tape? Wire nut? Something else entirely?
2. How to deal with mold/mildew in the wood and headliner where the old head unit used to be
3. How to unfreeze the headliner zippers
I guess this is how blog posts start. Thanks for the help, all. I'm not gonna hold it against Frank Langer that he cursed me with "this might be easier than it looks!"