Thanks for the above guidance using the XPath string, this helped solve the original question. The following replaces, in place, the original value on the line containing "2025-03-27 16:57:40 PDT" with "5" (as an example)

xmlstarlet ed -L --update "//database/comment()[contains(., '2025-03-27 16:57:40 PDT')]/following-sibling::row[1]/v" --value "5" test_modified.xml