URL Redirect Question - redirect old, established HTML page to new PHP page?

I have a site http://bodycleansediet.com that has a number of old htm/html pages.

These have good google search rankings which I don’t want to lose, but the pages look a mess and I want to tie them in with the rest of the site (php).

Could I just create the PHP page and then redirect the old htm/html?
Would this affect rankings?
How do I go about doing this?

An example of an old page is (warning its a mess!) http://http://www.bodycleansediet.com/isagenix-reviews/index.html

Thanks alot for your help, im a bit lost on this!

The two sticky posts at the top of this forum will show you how

Thanks Dan, my biggest concern is the affect of the redirect on rankings rather than the actual process itself (although those threads are very useful)

Will removing old pages and redirecting them to new pages affect rankings?

Cheers

Tom

As long as you send a 301 (moved permanently) header, you’ll be fine.