Godzilla, my new-to-me 68 Merc Colony Park. 121K miles. It was last driven in 1996 and had been sitting in the desert sun - ‘patina-ing’ - ever since, before my purchase 2 months ago. A person without electrical experience, or didn’t have a shop manual, created numerous electrical issues and caused the car to have been given up for dead. It’s now running (pretty well actually). It moves, and it stops - but I’ve only driven it about 30 feet. Getting the mechanicals into a safe status first, plus fixing the numerous electrical problems created by PO or their shop/mechanic. 102% rust free. Unmodified, except for the 40- Bazillion pound rated very old school frame trailer hitch. A survivor; though the interior, not so much.
Sounds like you are doing it right. That hot summer vacation it's been on could have caused any number of issues. Better to keep both of you safe and sound. Good to hear you are taking great care of your new baby. Enjoy.