You’ll find below a number of resources to help you to comply with GDPR. They are examples and advice, they should not be considered legal advice. These are early drafts, and so are really just for guidance as to structure.
The log book and document are the two key things. Feel free to download, but make sure you tailor to your own business (obviously!).
My advice would be to record everything you do, all changes you make, however small. And, in the document over do it, rather than under do it. I would err on the side of caution and make sure you cover yourself as much as possible.
If you want more help, or advice just get in touch.