404 error

I've just changed my permalinks from /%postname%/ to /%postname%.html So all links which are in /%postname%/ are showing 404 error. I want to redirect those links to /%postname%.html in order to avoid 404 error. Waiting for the response.

Hello Everyone, Is it bad for SEO to 301 redirect the errors you receive in Google Webmaster Tools? I changed my site recently and the old pages that were indexed are now returning 404 errors in Google Webmaster Tools. I've setup 301 redirects to forward to the homepage. Is that bad practice...

I can't see where else this should go so here it is. I have done a search and not found an appropriate answer. I have switched hosting to godaddy and now no-one can find my site. It comes up error 404 now I know google etc will have cached sites with the old isp address but is there a quick way...