How to use find and replace to replace a character with new line
You can click on the magnifying glass icon and choose Insert Pattern or press ⌃ CTRL+⌥ ALT+⌘ CMD+P
Then pick Line Break
A simple trick is to just copy the rest of a line and paste it into the "replace" field.
Works with Textedit, Xcode etc.
Find and Replace in Mac Pages version 8.0 doesn't have the 'Insert Pattern' as TextEdit does. Pages' Help does not provide information about how to use Paragraph Break, Line Break etc. But the following can be used:
\n for paragraph break
\i for line break
\t for tab
(found these out using 'Edit - Selection to Find')