How do I publish my professionally converted ePUB book?

How do I publish my ePUB book onto the Apple Bookstore from the UK? From what I've read so far I think I need to have a Preview / sample as the book will need to be purchased, but because the book is professionally converted into an ePub file by a specialist company (to ensure there was no problem with downloading it when people purchase it), I can't change it or take bits out of it as sample chapters etc. What should I do?

Thanks,

iGwyn