I recommend that you read the IBM Redbook called:
COM Toegther – with Domino
Only 158 pages if you read everything. You will only need to read about 80 pages to get started. This is an introduction to COM use with Domino.
This will give you the basics you need to write VB Code to open a Notes Database and get to all the methods and classes that you will need to access. I have done similar things with VBA code from Excel and Access. I have not done anythig with Rich Text Fields but it is possible to get the info that is in them.
Hope this helps