kmail can use the emails from your OE client. There are several threads on it once you come upon it. If you are confused once you get there, post up your question, I'll be happy to help.
As for your "favorites" I'd think you should be able to. However, it will probably be just copying over the html files from one directory to another depending on which browser you want. Since favorites are just links to the actual sites I don't see why not though