Finally, regarding the connection to external data: does using Flash to get or post data slow down the process?

Again, the answer to this depends on your final intentions (as mentioned above). Will you be using CGI (Common Gateway Interface), Perl, or HTML for your get/post commands, or will you be connecting to your external data using XML (Extensible Markup Language), CGI, Text files etc.?

If your site is entirely Flash-based, then the speed will depend on whether you'll be opening another Flash file with the retrieved data or whether the information will appear in the same Flash file already created.

I would recommend grabbing the backend data via Domino, as you would need little to no knowledge of XML, Javascript, or Flash. You may even want to consider using Dreamweaver with Domino, depending on how much of the backend information you require and how much should be sent back.

I hope this has given you some indication on the approach to take. Your decision should be based on the final results you are expecting from your Web site.