Cross-checking Without Breaking Anything
On the record
Claim what exists before creating anything new; duplicates are harder to remove than to avoid.
First pass
Set aside time to audit on a fixed schedule rather than treating it as a one-off project, which is worth planning around.
Mapping syndicated listings
Start by pulling every existing record into one sheet before changing anything.
On the record
Record the canonical version of the website field somewhere the operations team can find it.