Deal Maven questions for those who have completed KB I

I have to complete KB I with cert prior to my start date. I'm about half-way through the material and so far so good, nothing seems too hard. So my questions are:

1) Do you get to retake the case study quizzes as many times as you'd like (similar to the chapter quizzes) till you get a 100? Or is it a one and done, submit, final score type of deal?

2) How difficult is the model to build in comparison to the chapters (keep in mind I've only finished the first half - start DCF tomorrow), i.e. how hard is it to get certified? Have you ever heard of someone actually putting a legit effort into it and not getting certified?

3) Lastly, how long do you think the model would take for someone with no previous modeling experience to build it?

I ask because I only have about another week and a half where I'd be free to work on this, then I'm taking a two week vacation, then my internship starts. Therefore, if I don't get certified the first time around, it would be damn near impossible for me to re-submit and officially get certified prior to my start date (due to the fact that Deal Maven's turnaround on model evaluation is around a week according to the website, not to mention the fact that I'll be on vacation).

Essentially, do I need to bust my ass the next day or two to finish this with enough cush time to re-submit in the event the model isn't perfect or because the final model will take much longer to build and is much harder than any of the previous material? Or could I continue cruising (doing a little bit each day), hopefully finish it this weekend, submit and be okay?

Feel free to give any additional thoughts/advice. Thanks.