Maybe I don't understand what you're trying to accomplish but I don't see that XML needs to be involved. I'm no expert either but having revamped a website using PHP/MySQL about 18 months ago (www.italintl.com) it's not too difficult and maybe easier for you than for me considering you've dealt with ASP.

If you can export your database into a CSV document MySQL will allow you to import pretty easily especially with something like PHPMyAdmin as your database interface. A good host I've used that offers all this stuff in a basic but extensive (and very inexpensive) package is www.ace-host.net. I found starting with a good host that lays all this out in a very easy to use manner has really helped me in terms of learing what I need to know without being overwhelmed.

Hope this helps. Let me know if I can be of help in any way.

mktgbill