You can't really change your email address, but you can set up an alias. Not at the mac right now, so can't look for you, but look around for where you can set an alias -- mihgt have to go to the mobileme website. Then, you can use that alias, and all mail will come into your regular mailbox. You can color code the alias, so that if your mail shows a message in, say, green, you will know that it came to the alias.