Changing Permalink Structure

[rhyslud]

I am moving an existing site www.mandarinradio.com to a wordpress site on new server. I just redirected the DNS a few hours ago (and it has changed for me).

Last night in preparation, I used wordpress to recreate the 12 or so pages that were performing well. I edited the permalink structure of each to match the url that google likes:

"www.mandarinradio.com/good-page.htm"

I did not notice that it was converting those to

"www.mandarinradio.com/good-page-htm/"

because of my permalink structure choice.

Since it is only a few pages, I am considering changing my structure to %postname%.htm and then manually editing the permalinks in each post and page.

Two questions:

1. Is there any significant downside to the permalink structure above?
2. Will I somehow not be able to connect with and/or edit the permalinks of the pages I have already created? I am freaked out by the tutorial which states; "If you have already created posts on your site, then DO NOT change your permalink structure as your Posts will return 404 errors."