You'll certainly get the basics covered, Bart. Those courses are quite intense.
Plastering is one of those skills where it doesn't take a huge amount of instruction to get you started. After that, proficiency only comes through plenty of practice and repetition.
You'll certainly be able to work on "new work"..... ie new, straight walls etc.
Dealing with renovations and problem areas only comes with masses of experience, but everyone has to start somewhere.
After the course, by far the most popular route is to begin as a labourer, mixing up and serving a team... as Eddie has mentioned. I know plenty who have done this. You start by running around with buckets of plaster, then the time will come when one of them has several walls on, and they get you to do some finish trowelling to take the pressure off.
A lot of plasterers work single-handed. A labourer who only mixes and carries is much less use to them. Someone who can pitch in is invaluable. I see this all the time.
After a while, you're on the team, and they're looking for a new labourer. With the course under your belt, put your face about and simply ask.
No reason why you shouldn't get there. Good luck to you.