Also, instead of rebuilding the site from the "ground up", as I thought I might... I may be able to do some tweaking to the code that Yahoo Sitebuilder spit out to make it function as proper HTML, even though I'm FAR from an expert in HTML code! Mainly have to put the code into Notepad++, and adjust the hundreds of image links, because the images will be in slightly different directories than before. Also, need to delete the references to the Sitebuilder program that is in the code in every page.
I've never switched from one host to another before, nor changed domain registrars, so guess you could say that I'm learning the hard way...