Course re-run section and refs to it in others

@explorerleslie, @talbs please check for accuracy and completeness
@WatsonEmily please circulate to PMs for level of detail, other likely questions to address, format
@mhoeber , @srpearce please consider this a developmental/copy edit
@sarina, @nasthagiri if you have time I value your input also!

@zhkramer for MVP, it will be as above, but later that is def a known feature to add. @mslotkeEDX I'll add the xref.