Just go out and enjoy it Hann
I know of quite a few on here who have notched up a hundred miles.
Ady, Myself, Emma for sure. In fact I think she notched a few up for her Ironman training last year.
She may have some tips to offer
My tips are
Start steady
Good comfy saddle
Eat plenty
Drink lots of coca cola
Whats the furthest you have been Hann
I always find the bit between 70/ 85 miles the worst.