ACG - can't really add anything to the excellent advice you've already been given, except relax - take it easy - enjoy - and let us know how it went!
Don't panic, rest your body, your training will get you round 80% of the course and adrenalin will have you flying the other 20%!

And on the day ...

Some people will pass you; good luck to them - you may well see them later, in the SAG wagon, or by the roadside having bonked! Pace yourself and the fuel you take on board.

Some people will ride with you. Great stuff - people to chat to - and you get to talk bikes all day long!

Some people will struggle to keep up with you - that sweet, rewarding feeling as your powerful legs push on and leave them far behind.

You're going to have a great day. Just make sure you enjoy it as it'll whizz by so fast!