Metadata handling

I had an editor create the ePub file for my book. She used Jutoh which I didn’t like after hours trying. I’d like to make small modifications (words here and there) on my own to save me additional fees. I’m quite accustomed with the Unix/Linux vi editor and I’d be just happy making the modifications with it, if such thing was possible.

Because I had quite a few metadata issues having the same ePub file pass both Amazon and Apple verifications I’m a bit weary. Can I be assured that changing words in the ebook content (not styles, images, nor any other elements) using Calibre will not break anything else?