I can honestly say it was one of the hardest courses I have done, including GCSEs, A Levels (before the days when a toddler could pass one) and two degrees - but well worth it.
I did mine in 2003, and then CMCQ was part of the course.
We got told that you could instruct any weapon afterwards, but advised ringing up SASC beforehand if you are unsure on the weapon and they will help you go through it first.
The Regs do a much longer course, as they also do RMQ as part of the course and as has been said, they have the time to teach most weapons.
You are expected to know what you are talking about before you go, i.e. know the parts of the rifle/LSW, know the drills, know the fieldcraft. You are there to learn how to teach weapons, not to learn the weapons.
If Sully is still there, try to get into his syndicate...a very good teacher!
Oh yes, and the first day you are there is the only day you will have time to go out on. Others went out during the course and failed in spectacular style! The instructors will also have no problem RTUing you if you are unsafe/cr@p!!!