That whole thing works because the old timers at those stores actually pay attention to what works (they hear the same gripes all day). The tip is only half of it though, because you still have to go early before the word spreads and that side window gets just as bad as the main line. Next time bring the guy a coffee or something, since those little favors are how the good info keeps flowing.

Charge flat rate for sure, same job is same job. Had a batch of squealing AE-1s myself once, made bank doing them quick.

I get why you like the door, but I wouldn't count on it as your only line of defense. Those things are great until they aren't, and a timer or light sensor can act up in cold snaps when the battery gets weak or the track ices up. A raccoon is one thing, but a determined predator will keep working at a stuck door for hours, and you won't hear it from inside the house. Keeping a manual latch as a backup costs nothing and takes ten seconds before bed. We had a neighbor whose auto door quit closing after a hard freeze and he lost four hens in one night. Check the door every evening anyway, even with the timer.