200 Pages - Excel File Editing

I have a 200-page Excel workbook filled with client contact information. Many of the names, addresses, phone numbers, and emails are outdated, and I already have an up-to-date master list in a separate Excel file.

Your task is to cross-reference both files, replace any incorrect or missing contact details in the main workbook, and preserve its existing structure. No reformatting or formula work is required—this job is strictly about accurate data correction.

Please work directly in Microsoft Excel and use reliable lookup techniques (VLOOKUP, INDEX-MATCH, or Power Query—whatever you prefer) so every amended record matches the reference list exactly.

Deliverables:
• Cleaned 200-page workbook with all contact details updated
• A brief change log (sheet or txt) noting any rows you could not match unambiguously

I will supply both files immediately and am available to answer questions throughout the project.