[thelist] Switching file extensions from .html to .php, SEO consequences?

[Rich Points]

Howdy,
I have a large site with .html file extensions.  I'm developing some database futures that will require the passing of hidden variables.  I will likely do this via php.  I haven't investigated this yet but I'll probably add a line in my .htacess file redirecting .html pages to their .php equivalent.  

I'm curious how Google will re-index the site.  I suspect this will cause my page rank to drop or disappear but don't I know for sure.  Frankly I'm terrified to see this project through.

Has anyone done this out there?  I'm looking for advice for the best way to do this.  

Thanks

--
Rich Points
Rich at RichPoints.com
http://RichPoints.com