"certified' parts

Yes. The FAA says they need to be there, so they lie in the truck of
my car. However, my point is that when you get your private pilots
certificate you learn things like you need 3 landings in 90 days to
carry passengers, etc. People need to make the same effort when they
purchase an airplane. I'm sorry, but there is just no excluse for
buying a part at Autozone and thinking the FAA would bless it. If
you're going to invest the time/money in buying an airplane, and you're
going to do some of the work yourself, you really need to take the time
to learn the FARs associated with it.

-Robert, CFI