htaccess to the rescue
I struggled all day to figure out how to best handle the fact that all the pages on the site changed from .html to .php. I was concerned that anyone arriving from an old .html link would not get what they were after. After much digging and asking around, I discovered a simple directive in the Apache mod_alias module that saved the day.
One simple addition to my htaccess file was all that was necessary...
RedirectMatch (.*)\.html$ $1.php