Welcome to Tableau and welcome to our forums!
I've got a few resources for you, first a discussion about a similar question:
Info on editing the connection:
Info on using tabcmd to make these changes:
A lot of it comes down to personal preference but I tend to favor using windows scheduler and a tabcmd script to make the updates.
Hope this helps, and let us know if you have questions,
Happy New Year to you too!
This article describes how to update the password from Tableau Server: Edit Connections. Depending on how you've created and published the workbook/data source, you'll need to go to the 'Data Sources' tab of Tableau Server or of the actual workbook.
For (8), do you mean refreshing an extract that you've created from Oracle or Teradata? If so, you can refresh them on a schedule as described here: Add a Workbook or Data Source to a Schedule
Hope this helps!