TonyMExcel great questions—
(1) "Where do I begin in order to learn how to program and use Excel For the Web"
I'd recommend starting with the documentation for Office Scripts which can be found here:
http://aka.ms/office-scripts
Depending on your preference, the documentation has reference pages, tutorials, and sample projects which can get you going quickly.
(2) "Will my VBA code which is essentially a user interface with several user forms, easily convert wot Excel Web?"
This is a trickier one; currently, Excel for the Web does not (yet) have robust in-Workbook user interface components like buttons and forms. Depending on what you're trying to accomplish, you might be able to do is to use Power Automate with Microsoft Forms and the Excel connector's "Run script" action. This allows you to take Forms input and pass it to an Office Script which runs on your Workbook.
You can learn more about this here:
https://aka.ms/office-scripts/power-automate