I sent an email yesterday afternoon and received a reply today for
some additional work to be performed on my GPS-NAV (replace battery
with certification). I realize that they are a small company and I
hope they are busy making money, so I accept some reasonable delay in
communications.

I trust these guys to be reasonable and fair, so when I send them
work, I include a not exceed authorization to complete the repairs
with payment and return shipping information . That saves all the
extra communications and makes life easier for me and I am certain for
them too! If we were up flying, we would call this planning and
situational awareness. Great skills that also work on the ground.