Apollo Inertial Navigation

Can anyone help with following list of questions on the Apollo inertial
navigation systems?
I am fascinated by the challenges of inertial navigation faced by Apollo -
I've done some reading but so far haven't been able to find the answers to
these particular questions.

1. How much of a role did the inertial platform and guidance computer play
in navigation to the moon? How much of the navigation was done by ground
control and tracking?
2. Was the inertial system powered up continuously from launch through to
re-entry? Or was it only powered up to monitor and track the various engine
burns during the flight? Presumably once you are on the "right" trajectory,
there is nothing to disturb you until you get close to the moon/earth, so
you can power the system down until you need it again?
3. Was it necessary to re-set or correct platform alignment during the
flight, and if so, how often and how was this done - star shots?
4. With specific reference to the gyro's, how does the accuracy/drift
specification of the Apollo gyros compare to that of cheap fibre optic gyros
that one can purchase for about US$5k these days?
5. How does the accuracy of the shuttle system compare? If you are not going
to the moon, can you get by with lower accuracy?

Steve