UddeIM shouldn't be necessary. Private Messaging is built into CB. CBs private message notification can be modified using the language overrides feature shown below.
www.joomlapolis.com/blog/kyle/18701-language-overrides-have-arrived
There's a search feature on the language overrides page that you can use to find the language string then click it and it'll add an override for you to change it to whatever you like.