A project has a new name, and Word finds the old one dozens of times. Some occurrences may be in current instructions; others may be quotations or references to earlier work. The same text does not always call for the same edit.
Start with a copy and one replacement
Save a separate copy of the document. In Word's Find and Replace, enter both the old text and its replacement, then move through individual matches. Replace one intended occurrence and read the whole sentence. Check capitalisation, nearby punctuation and any formatting that matters.
Imagine a document containing “Map”, “Roadmap” and “Map archive”. Replacing the letters “map” without appropriate search options can reach beyond the project name. Matching whole words helps separate a name from part of another word; matching case distinguishes letter case. Neither option decides whether a historical reference should change.
Word's desktop and web interfaces differ. Use the search options available in your version rather than assuming that an advanced desktop setting exists in every interface.
Decide whether all really means all
If quotations must retain their wording, handle the matches individually. Replace All is useful only when every match within the chosen search scope should receive the same change. A large replacement count is a reason to inspect the result, not proof of a successful edit.
Search again for the old term and read a few passages containing the new one. Include a heading, a table and a sentence in ordinary body text if the document has them. If something changed unexpectedly, undo the operation promptly or return to the saved copy. Do not run a reverse global replacement: the replacement word may already have existed elsewhere.