what Blogger does not have server side language like php or the like, can not use the famous htacces but what you can do.:
Go WMT account, add your new domain with www and also without www.
Go to the old domain that must be wmt and sprocket the top right to give: Download site or something similar that says, I ask you to select another domain and you choose the new one you created ..
It also updates your sitemap and one thing:
If you had the old domain to the same blogger, recreates the url and put a meta-refresh tag eg redirect to the new domain while Google is accommodated.