Hi Petrichor. Where abouts are you?
It's not too much to ask. If you can film and record the stuff (you really don't want to be using an on-camera mic for the choir), someone could probably teach you how to do that with something like Sony Vegas Movie Studio in an afternoon. What software are you currently using?
If you have access, your local camcorder club may well have someone who will spend some time with you getting you going - in return for a donation to the club.
I'm a little surprised that the examiner will let you edit this though. I've filmed a number of seessions of teachers for assessment and the examiners most definitely don't want the content edited.