I just found and scanned the only chapter I ever received from the never-produced Qube 3 Developers Guide. It's the chapter that explains the Sausalito architecture; it does so pretty thoroughly and has a walkthrough of adding new services to the UI etc.

You can get it at http://www.cobaltfaqs.com/download/Qube3_Sausalito_architecture.pdf (1.4 MB)

It should be applicable for RaQ 550 as well AFAIK.