I found a little error in this page:
<menuchoice>View Image -> View Image</menuchoice>
<menuchoice>View -> View Image</menuchoice>
But the pages has been "Marked [...] for translation". Should I continue editing it or will this disturb translators?
You are right, it is wrong. I noticed it myself and corrected it.
You can allways edit a page even to modify existing text. Nothing will affect the translators until the new content is also marked for translation. At that point translators will need to have another look at the modified paragraphs, so it is actually an advantage to correct things as soon as possible.