[Building Sakai] Using gradebook in a project

[Alexander Bell]

I've been looking into this for a bit but I could use some pointers from 
someone who's implemented something similar already.

I want to make use of Sakai's gradebook in the Turnitin content review 
module, where I would read the grades of users returned from Turnitin 
and add them to 'x' user's entry in the sakai gradebook.
Coming from Blackboard development I would just use Blackboard's methods 
to load a score object for a user and persist a grade to it. But looking 
at Sakai I'm not sure whether I can do this using tools in 
sakai-gradebook-service-impl or if I have to implement something with 
sakai-gradebook-service-api. I haven't been able to find much in the way 
of documentation for using this. Is there a place you guys could recommend?

cheers