Pro tip: check the tiny shutter spring before you order 6 parts, a 4 day nightmare
Last month a guy brought in a Canon AE-1 from his late dad's closet in Sacramento, and the shutter would not fire past 1/60. I tore that thing down three separate times, cleaned every gear, ordered a new magnet and a fresh set of foam seals, and still nothing worked. I spent 4 nights squinting under my bench lamp with a loupe before I finally spotted it: one little spring near the mirror box had unhooked and was just sitting there, totally fine. Total time from drop off to working camera was 4 days, and the actual fix took 90 seconds with a pair of tweezers. The customer laughed and said his dad would have found it faster. Now I always check springs and levers before I touch the parts catalog, but I still feel dumb about the $38 I made him spend on stuff he did not need. What is your dumbest easy fix that you turned into a full teardown?