If their manual is available as a PDF download, you may be able to copy and paste chunks into Google Translate. I've done that successfully on other manuals. As long as the conversion to PDF wasn't done by simply scanning (resulting only in bitmap images), and if they didn't protect the document (as several radio manufacturers like to do on some of theirs), the text should be copyable.
Of course, if the BT functions are operated by voice recognition, you'll still have to learn some Japanese phrases.
