As Animal said.
Don’t worry to much about the gearbox, ok it’s a bit of the unknown for you. Christ so was unclipping my first girlfriends bra. I can do this with one hand and my eyes closed singing “She Loves You”.
I hadn’t driven anything bigger than a car when I went for my Class C. When I saw the gearbox on my induction 4 over 4 I thought I’ll never get that. But I did just like you will so deep breath and trust yourself and your instructor after all that’s what you are paying him for.
Best of luck.
Remember they can’t shoot you or make you pregnant that’s if your a bloke that is. Hey you never know.