Getting raw accelerometer data from wellness file

I'm looking to get the raw accelerometer data from an FIT wellness file for a particular date into a CSV to then make sense of it.

What would be the best course of action?

What is the granularity of the intervals in which the raw accelerometer values are recorded?  Any resources you can point me to would be helpful.

Is there any documentation about what the values each of the monitoring headers represent?  I can't seem to find it in the SDK documentation.