I was on QAIC 6 and was involved on the DS team for 7 and 8 but am not involved this year, as the course evolves slightly every year my information may be slightly out of date but should give you a good grounding at the least.
The course is quite intense, you have to commit to at least one, possibly two, training weekends every month from September through to April which will require you to travel to either Boscombe Down or Linton-on-Ouse. You will have a full schedule during the weekends usually working from the moment you arrive, 0900-2100 on the Saturday and until roughly 1600 on the Sunday. You will be challenged intellectually and be expected to improve regardless of your ability at the start of the course. It is likely you'll learn a lot about stuff you knew nothing about before so be prepared to find it hard!
A good way to prep for the selection weekend and the course in general would be to revise the fundamental principles of airmanship, air power, the history and structure of the RAF, your debating and public speaking skills and if you have the opportunity perhaps put some time into a flight sim. Public speaking is vitally important because a large part of the selection weekend hinges on it. A bit of practice in leadership and leadership exercises also wouldn't go amiss. I'm sure you're aware you have to be a master air cadet to apply for the course too.
The qualification you get out of QAIC is a Level 2 Award from the Institute of Leadership and Management. As far as I'm aware it doesn't carry any UCAS points but you can, and I did, add it to the 'other qualifications' section of your UCAS application. It's important to remember though that QAIC isn't a leadership course, unlike JL, which is why the qualification isn't of the same level. In my opinion the powers that be should look at getting the course accredited for a more relevant aviation related qualification but there we fo. QAIC as a whole will look good on a UCAS application, I mentioned it a fair bit and was given an unconditional offer by and am now studying at a respected Russell group university.
If you have any further questions feel free to ask.