I've managed to figure out how to get the LMS API, Set the Score and change Completion Status to complete
//get LMS API
var lmsAPI = parent;
//set score; the first number is the score
lmsAPI.SetScore(100, 100, 0);
//set Completion to "complete"
But I'm absolutely stuck on how to get the Success Status to change to Passed. Does anyone have a clue how to achieve this?