Hi Lola,
You will have no trouble using a semi auto gearbox car!
You can set it to 'auto change' meaning it does behave like an automatic or you can set it so that you change gears by either pushing the 'gear lever' up or down or if the car is more expensive and technologically advanced, via Paddles behind or around the steering wheel.
Our Smart Cars are semi auto and thats how they work, by default you're in 'manual' mode, and the car will not change gear until you flip the button for up. If you're at higher speeds and slow down, the gearbox will auto shift down to stop over revving of the engine/gearbox.
It's 'relatively' quick to get used to - and i'm pretty sure those 'basics' are what different manufacturers and designs are like pretty much across the board - things get more 'difficult' if you're buying a Sports Semi Auto a la Ferrari or Maserati or BMW M type car which have different programs and responsiveness to their gearboxes!
So which car you getting ? a Smart Car or a Ferrari 360 ?!!!
Hope this helps!
Dennis! West London & Slough UK!