Hi Tommy.
The assessment is all the paperwork needed to submit.
After this has been approved you will then be invited for the practical.
I did mine about 13 years ago. I was like you apprehensive as I was 43 when I took the practical.
It was all pretty straightforward and the assessors were very helpful. There not there to catch you out or anything. So long as you know a bit of everything you'll be fine.
Cheers Greg