It will not be stressful as Browns have been at it for many years with a great record.
Save your thinking for the day and listen to the guy who has done it many times before, your instructor.
You will have a great time but don't forget to go to the Orlando FAA, FSDO and get a validation of your UK license. Take your log book and medical with you. It will take 20-30min and is free.
Enjoy yourself.