Apache rewrite help, switched to .php extensions

Hi, folks:
this is a quick question for those who have done this before. I just added .php to my pretty URL/URIs to use an external tracking system that wouldn’t function with normal dynamic strings. This is NOT an SEO issue, but it’s something which had to be done.

So, my URLs have changed from:
mysite.com/2007/06/01/enc1379_230735
to
mysite.com/2007/06/01/enc1379_230735.php

I would like to add an Apache Mod Rewrite rule — separate from WordPress code — to have requests for the former posts redirect to the new location with .php added, but after looking at some docs online (we own our own servers), I am clueless as to the syntax to put this into the htaccess file without messing up pages and indexes, archives, etc.

Basically, I am willing to pay somebody to help me write a simple bit of code to add to the root htaccess file, which would redirect all queries for an old URL to the new one with .php added. I’m not concerned with Google since we use an XML sitemap and that will update; but I *am* concerned with things like social network tags (eg technorati, etc) and things like E! entertainment Online and C:net/news.com who have weitten about us and linked to specific pages. I have a custom 404 page in place which tells people to look in their browser and simple add .php to end of what is showing, but that’s not elegant.

Any urgent help (it’s June 2, 2007) on this would be most appeciated. Again, willing to pay the bucks for something that works, from somebody who isn’t experimenting.

HELP!

Christopher