Rob,
I don't think shifting will be an issue. I can drive a stick and have had ridden sportbikes for many years now. So, it will take me probably one lap to get it sorted and I'll be off and running. My concern is handling myself in a crowd of cars and not bouncing off all of them. So, just some feel for the car before hand will really help. I am going to schedule a test drive within the next few months. Then, once I get the car, I'll probably take it to some practice sessions and/or run the local autocross. Just to get comfortable.
Thanks,
Nate