Find and Replace
Since we do not yet have Find & Replace in Sites perhaps this method would help.
Highlight the text and copy it (CTRL-C).
Open Drive and start a new document.
Paste in the text (CTRL-V).
Use Find and Replace.
Copy the result and paste it back in the site.
Use find and replace in a document or presentation
On your computer, open a document or presentation in Google Docs or Google Slides.
Click Edit >> Find and replace.
Next to "Find," type the word you want to find. If you want to replace the word, enter the new word next to "Replace with."
To see the next time the word is used, click Next. To go back to the previous word, click Prev.
Optional: Narrow your search by using an option below.
Match case: Matches only words with the same capitalization.
Match using regular expressions: In Google Docs, matches words based on regular expressions.
To replace the highlighted word, click Replace. To replace the word every time it’s used, click Replace all.